Printed circuit board and method of manufacturing printed circuit board

ABSTRACT

A method for manufacturing a printed circuit board includes forming an opening portion in a substrate, positioning chip capacitors in the opening portion of the substrate such that the chip capacitors are accommodated in the opening portion of the substrate, forming a buildup structure including an interlayer resin insulating layer and a conductive layer over a surface of the substrate and the chip capacitors accommodated in the opening portion of the substrate, and forming on a surface of the buildup structure bump structures positioned to mount an IC chip such that the chip capacitors in the opening portion of the substrate are positioned directly below the IC chip.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of U.S. application Ser. No.12/784,634, filed May 21, 2010, which is a Divisional of and claimsbenefit of priority under 35 U.S.C. §120 from U.S. application Ser. No.11/777,841, filed Jul. 13, 2007, now U.S. Pat. No. 7,864,542, issuedJan. 4, 2011, the entire contents of each of which are herebyincorporated by reference. U.S. application Ser. No. 11/777,841 is aDivisional of and claims the benefit of priority under 35 U.S.C. §120from U.S. Ser. No. 10/780,856, filed Feb. 19, 2004, now U.S. Pat. No.7,342,803, issued Mar. 11, 2008, which is a Divisional of U.S. Ser. No.09/830,360 filed Apr. 25, 2001, now U.S. Pat. No. 6,724,638, issued Apr.20, 2004, which is the National Phase of International Application No.PCT/JP00/05970 filed Sep. 1, 2000. International Application No.PCT/JP00/05970 is based upon and claims benefit of priority under 35U.S.C §119 from Japanese Application Nos. JP 11-248311 filed Sep. 2,1999; JP 11-369003 filed Dec. 27, 1999; JP 2000-221350 filed Jul. 21,2000; JP 2000-230868 filed Jul. 31, 2000; JP 2000-230869 filed Jul. 31,2000 and JP 2000-230870 filed Jul. 31, 2000.

TECHNICAL FIELD

The present invention relates to a printed board for mounting thereonelectronic components such as an IC chip and a method of manufacturingthe printed board. More particularly, the present invention relates to aprinted circuit board including therein a capacitor or the like and amethod of manufacturing the printed circuit board.

BACKGROUND ART

At present, for the purpose of smoothly supplying electric power to anIC chip, a chip capacitor is often mounted on the surface of a printedcircuit board used as a package substrate.

The reactance of a wiring from the chip capacitor to the IC chip dependson frequency. Due to this, as IC chip driving frequency increases, thechip capacitor cannot exhibit sufficient effect even if the chipcapacitor is mounted on the surface of the printed circuit board.Considering this, the applicant of the present invention proposed atechnique, identified as Japanese Patent Application No. 11-248311, forforming a concave portion on a core substrate so as to contain therein achip capacitor. Techniques for embedding a capacitor in a substrate aredisclosed in Japanese Patent Unexamined Application Publication (to bereferred to as “Publication” hereinafter) Nos. 6-326472, 7-263619,10-256429, 11-45955, 11-126978, 11-312868 and the like.

Publication No. 6-326472 discloses a technique for embedding a capacitorin a resin substrate made of glass epoxy. With this constitution, it ispossible to reduce power supply noise and to dispense with a space formounting the chip capacitor, thereby making an insulating substratesmall in size. Publication No. 7-263619 discloses a technique forembedding a capacitor in a substrate made of ceramic, alumina or thelike. With this constitution, the capacitor is connected between a powersupply layer and a ground layer to thereby shorten wiring length andreduce wiring inductance.

However, according to the Publication Nos. 6-326472 and 7-263619 statedabove, the distance from the IC chip to the capacitor cannot be set tooshort and the wiring inductance cannot be reduced as currently desiredin the higher frequency region of the IC chip. In case of a multi-layerbuildup wiring board made of resin, in particular, due to the differencein the coefficient of thermal expansion and a capacitor made of ceramicand a core substrate as well as interlayer resin insulating layers madeof resin, disconnection occurs between the terminal of the chipcapacitor and a via, separation occurs between the chip capacitor andthe interlayer resin insulating layers and cracks occur to theinterlayer resin insulating layers. Thus, the multi-layer buildup wiringboard could not realize high reliability for a long time.

On the other hand, according to the invention of Publication No.11-248311, if the position at which a capacitor is arranged is deviated,the connection between the terminal of the capacitor and a via cannot beaccurately established and power cannot be possibly supplied from thecapacitor to the IC chip.

The present invention has been made to solve the above-stated problems.It is, therefore, an object of the present invention to provide aprinted circuit board including therein a capacitor and having enhancedconnection reliability and to provide a method of manufacturing theprinted circuit board.

DISCLOSURE OF THE INVENTION

In order to achieve the above purpose, a printed circuit boardconstituted by alternately laminating interlayer resin insulating layersand conductive circuits in a multilayer manner on a core substratecontaining a capacitor, characterized in that

the core substrate containing said capacitor is constituted by providinga first resin substrate, a second resin substrate having an opening forcontaining the capacitor and a third resin substrate in a multilayermanner while interposing bonding plates.

A printed circuit board manufacturing method characterized by comprisingat least the following steps (a) to (d):

(a) forming a conductor pad section on a first resin substrate;(b) connecting a capacitor to said conductor pad section of said firstresin substrate through a conductive bonding agent;(c) providing a third resin substrate, a second resin substrate havingan opening for containing said capacitor and said first resin substratein a multilayer manner while interposing bonding plates so that saidcapacitor of said first resin substrate is contained in said opening ofsaid second resin substrate and that said opening of said second resinsubstrate is closed by the third resin substrate; and(d) heating and pressurizing said first resin substrate, said secondresin substrate and said third resin substrate, to thereby provide acore substrate.

According to a printed circuit board and a printed circuit boardmanufacturing method, the capacitor can be contained in the coresubstrate and the distance between the IC chip and the capacitor isshortened. Therefore, it is possible to reduce the loop inductance ofthe printed circuit board. Further, since the core substrate isconstituted by providing resin substrates in a multilayer manner, it canobtain sufficient strength. Besides, since the core substrate isconstituted smoothly by providing the first resin substrate and thethird resin substrate on the both sides of the core substrate,respectively, it is possible to appropriately form interlayer resininsulating layers and conductor circuits on the core substrate and tothereby decrease the probability of the occurrence of defective printedcircuit boards.

Interlayer resin insulating layers are provided on the core substrate,via holes or through holes are provided in the interlayer resininsulating layers, and conductor circuits serving as conductive layersare formed, which means the circuit is formed by a buildup method. Asthe buildup method, either a semi-additive method, a full additivemethod can be employed.

It is preferable that a gap is filled with a resin. By removing the gapbetween the capacitor and the core substrate, the capacitor included inthe core substrate behaves less frequently. Even if a stress resultingfrom the capacitor occurs, the stress can be eased by the filled resin.Also, the resin can advantageously bond the capacitor to the coresubstrate and prevent migration.

Each of the bonding plates may have a core impregnated with athermosetting resin. Due to this, the core substrate can obtain highstrength.

Each of the first, second and third resin substrates may have a coreimpregnated with a resin. Due to this, the core substrate can obtainhigh strength.

A plurality of capacitors may be contained in the core substrate. Due tothis, it is possible to highly integrate the capacitors.

The conductor circuits may be formed on the second resin substrate. Dueto this, it is possible to increase the wiring density of the substrateand to reduce the number of interlayer resin insulating layers.

The capacitor may be contained in the substrate and, at the same time, acapacitor is provided on the surface of the printed circuit board. Sincethe capacitor is contained in the printed circuit board, the distancebetween the IC chip and the capacitor is shortened, loop inductance isreduced and power can be supplied momentarily. Since the capacitor isalso provided on the surface of the printed circuit board, a massstorage capacitor can be attached and high power can be easily suppliedto the IC chip.

The capacitance of the capacitor on the surface may be equal to orhigher than that of a capacitor on an inner layer. Due to this, it ispossible to ensure the desired operation of the IC chip without lack ofpower supply in a high frequency region.

The inductance of the capacitor on the surface may be equal to or higherthan that of the capacitor on an inner layer. Due to this, it ispossible to ensure the desired operation of the IC chip without lack ofpower supply in a high frequency region.

The electrode of the chip capacitor on which the metal film may beformed is made electrically connectable using a via hole made of aplated material. Here, the electrode of the chip capacitor is made bymetalization and has irregular portions on the surface thereof. However,the surface of the chip capacitor is smoothed by the metal film anddisconnection does not occur to the electrode, the bonding plates or thelike even if a heat cycle test is conducted.

The metal film of the electrode of the capacitor is preferably made ofone selected from copper, nickel and noble metal. This is because alayer made of tin or zinc tends to induce migration to the capacitorincluded in the substrate. For that reason, the metal film can alsoprevent the occurrence of migration.

Further, the surface of the chip capacitor may be roughed. By doing so,the adhesiveness between the chip capacitor made of ceramic and thebonding layer, the interlayer resin insulating layers made of a resin ishigh and the separation of the bonding layers and the interlayer resininsulating layers does not occur to interfaces even if a heat cycle testis conducted.

At least a part of a coating layer of the electrode of the capacitor mybe exposed and contained in the printed circuit board to thereby makethe electrode exposed from the coating layer electrically connectable.In this case, it is preferable that the metal exposed from the coatinglayer mainly consists of copper. This is because connection resistancecan be reduced.

A chip capacitor having electrodes formed inside of an outer edgethereof may be employed. Due to this, even if continuity is establishedthrough the via hole, a large external electrode can be provided and theallowable range of alignment is widened, so that connection defect canbe eliminated.

A capacitor having electrodes formed in a matrix may be employed. Due tothis, a large chip capacitor can be contained in the core substrate.Accordingly, capacitance can be increased and electrical problems canbe, therefore, solved. Besides, even if going through various heathistories, the printed circuit board does not warp so easily.

A plurality of chip capacitors for providing many capacitors may becoupled to be employed as the capacitor. By doing so, it is possible toappropriately adjust capacitance and to appropriately operate the ICchip.

The coefficient of thermal expansion of the insulating bonding agent maybe set lower than that of the containing layer, i.e., set closer to thatof the capacitor made of ceramic. Due to this, even if an internalstress resulting from the difference in the coefficient of thermalexpansion between the core substrate and the capacitor occurs in a heatcycle test, cracks, separation and the like less occur to the coresubstrate, thereby making it possible to attain high reliability.

To obtain the above-stated object, a printed circuit board may beconstituted by providing resin insulating layers and conductor circuitson a core substrate in a multilayer manner, technically characterized inthat

the core substrate is constituted by bonding together a plurality ofresin substrates, the conductor circuits formed on the plurality ofresin substrates; and

a capacitor is contained in the core substrate.

A printed circuit board may be constituted by providing resin insulatinglayers and conductor circuit on a core substrate in a multilayer manner,technically characterized in that

the core substrate is constituted by bonding together a plurality ofresin substrates, the conductor circuits formed on the plurality ofresin substrates; and

a capacitor is contained in a concave portion formed in the coresubstrate.

The capacitor can be contained in the core substrate and the distancebetween the IC chip and the capacitor is shortened. Due to this, it ispossible to reduce the loop inductance of the printed circuit board. Inaddition, since the core substrate is formed by providing a plurality ofresin substrates on which the conductor circuits are formed in amultilayer manner, the wiring density of the core substrate is increasedand the number of interlayer resin insulating layers can be reduced.

Interlayer resin insulating layers are provided on the core substrate,via holes or through holes are provided in the interlayer resininsulating layers, and conductor circuits serving as conductive layersare formed, which means a circuit formed by a buildup method. As thebuildup method, either a semi-additive method, a full additive methodcan be employed.

It is preferable that a gap is filled with a resin. By removing the gapbetween the capacitor and the core substrate, the capacitor included inthe core substrate behaves less frequently. Even if a stress resultingfrom the capacitor occurs, the stress can be eased by the filled resin.Also, the resin can advantageously bond the capacitor to the coresubstrate and prevent migration.

A plurality of resin substrates may be bonded together with bondingplates interposed therebetween. Due to this, it is possible to stronglybond the resin substrates together.

Each of the bonding plates may have a core impregnated with athermosetting resin. Due to this, the core substrate can obtain highstrength.

Each of the resin substrates may have a core impregnated with a resin.Due to this, the core substrate can obtain high strength.

A plurality of capacitors may be contained in the core substrate. Due tothis, it is possible to highly integrate the capacitors.

The capacitor may be contained in the substrate and, at the same time, acapacitor is provided on the surface of the printed circuit board. Sincethe capacitor is contained in the printed circuit board, the distancebetween the IC chip and the capacitor is shortened, loop inductance isreduced and power can be supplied momentarily. Since the capacitor isalso provided on the surface of the printed circuit board, a massstorage capacitor can be attached and high power can be easily suppliedto the IC chip.

The capacitance of the capacitor on the surface may be equal to orhigher than that of a capacitor on an inner layer. Due to this, it ispossible to ensure the desired operation of the IC chip without lack ofpower supply in a high frequency region.

The inductance of the capacitor on the surface may be equal to or higherthan that of the chip capacitor on an inner layer. Due to this, it ispossible to ensure the desired operation of the IC chip without lack ofpower supply in a high frequency region.

The electrode of the chip capacitor on which the metal film is formedmay be made electrically connectable using a via hole made of a platedmaterial. Here, the electrode of the chip capacitor is made bymetalization and has irregular portions on the surface thereof. However,since the surface of the chip capacitor is smoothed by the metal filmand the via hole is formed, resin residue does not remain when a throughhole is formed in the resin coated on the electrode and the reliabilityof the connection between the via hole and the electrode can beenhanced. Further, since the via hole is formed by plating in theelectrode having a plated member formed thereon, the characteristics ofthe connection between the electrode and the via hole is high anddisconnection does not occur between the electrode and the via hole evenif a heat cycle test is conducted.

The metal film of the electrode of the capacitor is preferably made ofone selected from copper, nickel and noble metal. This is because alayer made of tin or zinc tends to induce migration to the capacitorincluded in the substrate. For that reason, the metal film can alsoprevent the occurrence of migration.

Further, the surface of the chip capacitor may be roughed. By doing so,the adhesiveness between the chip capacitor made of ceramic and thebonding layer, the interlayer resin insulating layers made of a resin ishigh and the separation of the interlayer resin insulating layers doesnot occur to interfaces even if a heat cycle test is conducted.

At least a part of a coating layer of the electrode of the capacitor maybe exposed and contained in the printed circuit board to thereby makethe electrode exposed from the coating layer electrically connectable.In this case, it is preferable that the metal exposed from the coatinglayer mainly consists of copper. This is because high connectioncharacteristics can be ensured and connection resistance can be reducedeven if a metal layer is formed by plating on the exposed metal.

A chip capacitor having electrodes formed inside of an outer edgethereof may be employed. Due to this, even if continuity is establishedthrough the via hole, a large external electrode can be provided and theallowable range of alignment is widened, so that connection defect canbe eliminated.

A capacitor having electrodes formed in a matrix may be employed. Due tothis, a large chip capacitor can be contained in the core substrate.Accordingly, capacitance can be increased and electrical problems canbe, therefore, solved. Besides, even if going through various heathistories, the printed circuit board does not warp so easily.

A plurality of chip capacitors for providing many capacitors may becoupled to be employed as the capacitor. By doing so, it is possible toappropriately adjust capacitance and to appropriately operate the ICchip.

The coefficient of thermal expansion of the insulating bonding agent maybe set lower than that of the core substrate, i.e., set closer to thatof the capacitor made of ceramic. Due to this, even if an internalstress resulting from the difference in the coefficient of thermalexpansion between the core substrate and the capacitor occurs in a heatcycle test, cracks, separation and the like less occur to the coresubstrate, thereby making it possible to attain high reliability.

A printed circuit board manufacturing method may be characterized bycomprising at least the following steps (a) to (e):

(a) forming conductor circuits on a plurality of resin substrates;(b) providing a plurality of said resin substrates in a multilayermanner through bonding plates;(c) bonding together said resin substrates through said bonding plates,to thereby provide a core substrate;(d) forming a concave portion in said core substrate; and(e) containing a capacitor in said concave portion.

A printed circuit board manufacturing method may include at least thefollowing steps (a) to (e):

(a) forming a resin substrate with a through hole and having a conductorcircuit provided on a surface;(b) forming a resin substrate without a through hole and having aconductor circuit provided on a surface;(c) providing said resin substrate with the through hole and said resinsubstrate without the through hole through a bonding plate in amultilayer manner;(d) bonding together said resin substrates through said bonding plate,to thereby provide a core substrate; and(e) containing a capacitor in said concave portion.

The capacitor can be contained in the core substrate and the distancebetween the IC chip and the capacitor is shortened. Therefore, it ispossible to reduce the loop inductance of the printed circuit board.Also, since the core substrate is formed by providing a plurality ofresin substrates, on which conductor circuits are formed, in amultilayer manner, wiring density within the core substrate is increasedand the number of interlayer resin insulating layers can be reduced.

In order to achieve the above purpose, a printed circuit board may beconstituted by alternately providing interlayer resin insulating layersand conductor circuits in a multilayer manner on a core substratecontaining a capacitor, characterized in that

the core substrate containing said capacitor is constituted by providinga first resin substrate, a second resin substrate having an opening forcontaining the capacitor and a third resin substrate in a multilayermanner while interposing bonding plates; and

via holes connected to a terminal of said capacitor are provided on bothsides of said core substrate.

The capacitor can be contained in the core substrate and the distancebetween the IC chip and the capacitor is shortened. Therefore, it ispossible to reduce the loop inductance of the printed circuit board.Further, since the core substrate is constituted by providing resinsubstrates in a multilayer manner, it can obtain sufficient strength.Besides, since the core substrate is constituted smoothly by providingthe first resin substrate and the third resin substrate on the bothsides of the core substrate, respectively, it is possible toappropriately form interlayer resin insulating layers and conductorcircuits on the core substrate and to thereby decrease the probabilityof the occurrence of defective printed circuit boards. Further, sincethe via holes are provided on the both sides of the core substrate, itis possible to connect the IC chip to the capacitor and an externalconnection substrate to the capacitor with shortest distances and it ispossible to momentarily supply high power from the external connectionsubstrate to the IC chip.

Interlayer resin insulating layers are provided on the core substrate,via holes or through holes are provided in the interlayer resininsulating layers, and conductor circuits serving as conductive layersare formed, which means the circuit is formed by a buildup method. Asthe buildup method, either a semi-additive method, a full additivemethod can be employed.

Further, by arranging connection wirings, it is possible to providewirings below the capacitor. As a result, the degree of freedom forwirings increases, thereby making it possible to realize high densityand make the printed circuit board small in size.

It is preferable that a resin is filled between the capacitor and thesubstrate. By removing the gap between the capacitor and the substrate,the capacitor included in the core substrate behaves less frequently.Even if a stress resulting from the capacitor occurs, the stress can beeased by the filled resin. Also, the resin can advantageously bond thecapacitor to the core substrate and prevent migration.

Each of the bonding plates may have a core impregnated with athermosetting resin. Due to this, the core substrate can obtain highstrength.

Each of the first, second and third resin substrates may have a coreimpregnated with a resin. Due to this, the core substrate can obtainhigh strength. For example, a core impregnated with a reinforcingmaterial such as glass epoxy or glass phenol can be employed.

Since a plurality of capacitors may be contained in the core substrate,it is possible to highly integrate the capacitors. It is, therefore,possible to ensure more capacitance.

The conductor circuits may be formed on the second resin substrate. Dueto this, it is possible to increase the wiring density of the substrateand to reduce the number of interlayer resin insulating layers.

The capacitor may be contained in the substrate and, at the same time, acapacitor is provided on the surface of the printed circuit board. Sincethe capacitor is contained in the printed circuit board, the distancebetween the IC chip and the capacitor is shortened, loop inductance isreduced and power can be supplied momentarily. Since the capacitor isalso provided on the surface of the printed circuit board, a massstorage capacitor can be attached and high power can be easily suppliedto the IC chip.

The capacitance of the capacitor on the surface may be equal to orhigher than that of a capacitor on an inner layer. Due to this, it ispossible to ensure the desired operation of the IC chip without lack ofpower supply in a high frequency region.

The inductance of the capacitor on the surface may be equal to or higherthan that of the capacitor on an inner layer. Due to this, it ispossible to ensure the desired operation of the IC chip without lack ofpower supply in a high frequency region.

The electrode of the chip capacitor on which the metal film is formedmay be made electrically connectable using a via hole made of a platedmaterial. Here, the electrode of the chip capacitor is made bymetalization and has irregular portions on the surface thereof. However,since the surface of the chip capacitor is smoothed by the metal filmand the via hole is formed, resin residue does not remain when a throughhole is formed in the resin coated on the electrode and the reliabilityof the connection between the via hole and the electrode can beenhanced. Further, since the via hole is formed by plating in theelectrode having a plated member formed thereon, the characteristics ofthe connection between the electrode and the via hole is high anddisconnection does not occur between the electrode and the via hole evenif a heat cycle test is conducted.

The metal film of the electrode of the capacitor is preferably made ofone selected from copper, nickel and noble metal. This is because alayer made of tin or zinc tends to induce migration to the capacitorincluded in the substrate. For that reason, the metal film can alsoprevent the occurrence of migration.

Further, the surface of the chip capacitor may be roughed. By doing so,the adhesiveness between the chip capacitor made of ceramic and thebonding layer, the interlayer resin insulating layers made of a resin ishigh and the separation of the bonding layers and the interlayer resininsulating layers does not occur to interfaces even if a heat cycle testis conducted.

At least a part of a coating layer of the electrode of the capacitor maybe exposed and contained in the printed circuit board to thereby makethe electrode exposed from the coating layer electrically connectable.In this case, it is preferable that the metal exposed from the coatinglayer mainly consists of copper. This is because high connectioncharacteristics can be ensured and connection resistance can be reducedeven if a metal layer is formed by plating on the exposed metal.

A chip capacitor having electrodes formed inside of an outer edgethereof may be employed. Due to this, even if continuity is establishedthrough the via hole, a large external electrode can be provided and theallowable range of alignment is widened, so that connection defect canbe eliminated.

A chip capacitor having electrodes formed in a matrix may be employed.Due to this, a large chip capacitor can be contained in the coresubstrate. Accordingly, capacitance can be increased and electricalproblems can be, therefore, solved. Besides, even if going throughvarious heat histories, the printed circuit board does not warp soeasily.

A plurality of chip capacitors for providing many capacitors may becoupled to be employed as the capacitor. By doing so, it is possible toappropriately adjust capacitance and to appropriately operate the ICchip.

The coefficient of thermal expansion of the insulating bonding agent maybe set lower than that of the containing layer, i.e., set closer to thatof the capacitor made of ceramic. Due to this, even if an internalstress resulting from the difference in the coefficient of thermalexpansion between the core substrate and the capacitor occurs in a heatcycle test, cracks, separation and the like less occur to the coresubstrate, thereby making it possible to attain high reliability.

A printed circuit board manufacturing method may be characterized bycomprising at least the following steps (a) to (d):

(a) attaching a capacitor to a first resin substrate through a bondingmaterial;(b) providing a third resin substrate, a second resin substrate havingan opening for containing said capacitor and a first resin substrate ina multilayer manner so that said capacitor of said first resin substrateis contained in said opening of said second substrate and that saidopening of said second resin substrate is closed by said third resinsubstrate, thereby providing a core substrate;(c) applying laser and forming a via hole opening reaching saidcapacitor in said core substrate; and(d) forming a via hole in said via hole opening.

The capacitor can be contained in the core substrate and the distancebetween the IC chip and the capacitor is shortened. Therefore, it ispossible to reduce the loop inductance of the printed circuit board.

A printed circuit board manufacturing method may be characterized bycomprising at least the following steps (a) to (f):

(a) forming a via hole formation opening in a metal film on one side ofa first resin substrate;(b) attaching a capacitor to a metal film unformed surface of said firstresin substrate through a bonding material;(c) providing a third resin substrate, a second resin substrate havingan opening for containing said capacitor and said first resin substratein a multilayer manner by interposing bonding plates so that saidcapacitor of said first resin substrate is contained in said opening ofsaid second resin substrate and that said opening of said second resinsubstrate is closed by said third resin substrate;(d) heating and pressurizing said first resin substrate, said secondresin substrate and said third resin substrate, to thereby provide acore substrate;(e) applying laser to said via hole formation opening formed in saidmetal film of said first resin substrate, and forming a via hole openingreaching said capacitor; and(f) forming a via hole in said via hole opening.

The capacitor can be contained in the core substrate and the distancebetween the IC chip and the capacitor is shortened. Therefore, it ispossible to reduce the loop inductance of the printed circuit board. Inaddition, an opening is provided in the metal film of the first resinsubstrate having the metal film formed on one side thereof by etching orthe like. By applying laser to the position of the opening, the resininsulating layer exposed from the opening is removed and an opening fora via hole is provided. As a result, the opening diameter of the viahole depends on the opening diameter of the metal film, so that it ispossible to form the via hole to have an appropriate opening diameter.Likewise, the positional accuracy of the via hole opening depends on theopening position of the metal film. Due to this, even if the positionalaccuracy of the laser application is low, it is possible to form the viahole at an appropriate position.

A printed circuit board manufacturing method may be characterized bycomprising at least the following steps (a) to (f):

(a) forming via hole formation openings in metal films of a first resinsubstrate and a third resin substrate, the metal films bonded on onesides of said first resin substrate and said third resin substrate,respectively;(b) attaching a capacitor to a metal film unformed surface of said firstresin substrate through a bonding material;(c) providing said third resin substrate, a second resin substratehaving an opening for containing said capacitor and said first resinsubstrate in a multilayer manner by providing a bonding plate on saidmetal film unformed surface so that said capacitor of said first resinsubstrate is contained in said opening of said second resin substrateand that said opening of said second resin substrate is closed by saidthird resin substrate;(d) heating and pressurizing said first resin substrate, said secondresin substrate and said third resin substrate, to thereby provide acore substrate;(e) applying laser to said via hole formation openings formed in saidfirst resin substrate and said third resin substrate, and forming a viahole opening reaching said capacitor; and(f) forming a via hole in said via hole opening.

The capacitor can be contained in the core substrate and the distancebetween the IC chip and the capacitor is shortened. Therefore, it ispossible to reduce the loop inductance of the printed circuit board. Inaddition, openings are provided in the metal films of the first andthird resin substrates each having the metal film formed on one sidethereof, respectively, by etching or the like. By applying laser to theposition of the opening, the resin insulating layer exposed from theopening is removed and an opening for a via hole is provided. As aresult, the opening diameter of the via hole depends on the openingdiameter of the metal film, so that it is possible to form the via holeto have an appropriate opening diameter. Likewise, the positionalaccuracy of the via hole opening depends on the opening position of themetal film. Due to this, even if the positional accuracy of the laserapplication is low, it is possible to form the via hole at anappropriate position.

Further, since the core substrate is constituted by providing resinsubstrates in a multilayer manner, it can obtain sufficient strength.Besides, since the core substrate is constituted smoothly by providingthe first resin substrate and the third resin substrate on the bothsides of the core substrate, respectively, it is possible toappropriately form interlayer resin insulating layers and conductorcircuits on the core substrate and to thereby decrease the probabilityof the occurrence of defective printed circuit boards. Further, sincethe via holes are provided on the both sides of the core substrate, itis possible to connect the IC chip to the capacitor and an externalconnection substrate to the capacitor with shortest distances and it ispossible to momentarily supply high power from the external connectionsubstrate to the IC chip.

A printed circuit board manufacturing method may be characterized bycomprising at least the following steps (a) to (g):

(a) forming a through hole formation openings in metal films of a firstresin substrate and a third resin substrate, the metal films bonded onone sides of said first resin substrate and said third resin substrate,respectively;(b) attaching a capacitor to a metal film unformed surface of said firstresin substrate through a bonding material;(c) providing said third resin substrate, a second resin substratehaving an opening for containing said capacitor and said first resinsubstrate in a multilayer manner by providing a bonding plate on saidmetal film unformed surface so that said capacitor of said first resinsubstrate is contained in said opening of said second resin substrateand that said opening of said second resin substrate is closed by saidthird resin substrate;(d) heating and pressurizing said first resin substrate, said secondresin substrate and said third resin substrate, to thereby provide acore substrate;(e) applying laser to said through hole formation openings formed insaid first resin substrate and said third resin substrate, and forming avia hole opening reaching said capacitor;(f) removing or thinning said metal films; and(g) forming a conductor circuit and a via hole on said core substrate.

The capacitor can be contained in the core substrate and the distancebetween the IC chip and the capacitor is shortened. Therefore, it ispossible to reduce the loop inductance of the printed circuit board. Inaddition, an opening is provided in the metal film of the first resinsubstrate having the metal film formed on one side thereof by etching orthe like. By applying laser to the position of the opening, the resininsulating layer exposed from the opening is removed and an opening fora via hole is provided. Thereafter, the metal film is removed by etchingor the like. As a result, the opening diameter of the via hole dependson the opening diameter of the metal film, so that it is possible toform the via hole to have an appropriate opening diameter. Likewise, thepositional accuracy of the via hole opening depends on the openingposition of the metal film. Due to this, even if the positional accuracyof the laser application is low, it is possible to form the via hole atan appropriate position. In addition, by removing the metal film byetching or the like, wirings can be formed thin and, therefore, formedat fine pitch.

Further, since the core substrate is constituted by providing resinsubstrates in a multilayer manner, it can obtain sufficient strength.Besides, since the core substrate is constituted smoothly by providingthe first resin substrate and the third resin substrate on the bothsides of the core substrate, respectively, it is possible toappropriately form interlayer resin insulating layers and conductorcircuits on the core substrate and to thereby decrease the probabilityof the occurrence of defective printed circuit boards.

In order to achieve the above purpose, a printed circuit board may beconstituted by providing resin insulating layers and conductor circuitson a core substrate in a multilayer manner, characterized in that

a capacitor is included in said core substrate, and a relatively largelower-layer via hole connected to an electrode of said capacitor isformed; and

a plurality of relatively small upper-layer via holes connected to onesaid lower-layer via hole are provided in an interlayer resin insulatinglayer on an upper surface of said core substrate.

A capacitor may be included in the core substrate, a relatively largelower-layer via hole connected to a terminal of the capacitor is formed,and a plurality of relatively small upper-layer via holes connected toone the lower-layer via hole are provided in an interlayer resininsulating layer on an upper surface of the core substrate. By doing so,it is possible to connect the terminal of the capacitor to thelower-layer via holes even if the position at which the capacitor isprovided is shifted, and it is possible to ensure the supply of powerfrom the capacitor to the IC chip. Further, by providing a plurality ofrelatively small upper-layer via holes, it is possible to obtain thesame effect as that of connecting inductances in parallel. Thus, thehigh frequency characteristics of power supply lines and ground linesare enhanced, thereby making it possible to prevent the malfunction ofthe IC chip due to lack of supply of power or the variation of earthlevel. Moreover, since the wiring length can be shortened, it ispossible to reduce loop inductance.

It is preferable that a concave portion is filled with a resin. Byremoving the gap between the capacitor and the core substrate, thecapacitor included in the core substrate behaves less frequently. Evenif a stress resulting from the capacitor occurs, the stress can be easedby the filled resin. Also, the resin can advantageously bond thecapacitor to the core substrate and prevent migration.

A filled via hole having a flat surface may be employed as thelower-layer via hole. Due to this, it is possible to directly connect aplurality of upper-layer via holes to one lower-layer via hole. Thus, itis possible to enhance the characteristics of the connection between thelower-layer via hole and the upper-layer via hole and to thereby ensurethe supply of power from the capacitor to the IC chip.

One capacitor may be contained in a concave portion formed in the coresubstrate. Thus, the capacitor is arranged in the core substrate, sothat the distance between the IC chip and the capacitor is shortened andit is possible to reduce the loop inductance of the printed circuitboard.

A plurality of capacitors may be contained in the concave portion. Dueto this, it is possible to realize the high integration of capacitors.

The electrode of the chip capacitor on which the metal film is formedmay be made electrically connectable using a via hole made of a platedmaterial. Here, the electrode of the chip capacitor is made bymetalization and has irregular portions on the surface thereof. However,since the surface of the chip capacitor is smoothed by the metal filmand the via hole is formed, resin residue does not remain when a throughhole is formed in the resin coated on the electrode and the reliabilityof the connection between the via hole and the electrode can beenhanced. Further, since the via hole is formed by plating in theelectrode having a plated member formed thereon, the characteristics ofthe connection between the electrode and the via hole is high anddisconnection does not occur between the electrode and the via hole evenif a heat cycle test is conducted.

The surface of the chip capacitor may be roughed. By doing so, theadhesiveness between the chip capacitor made of ceramic and the bondinglayer, the interlayer resin insulating layers made of a resin is highand the separation of the bonding layers and the interlayer resininsulating layers does not occur to interfaces even if a heat cycle testis conducted.

At least a part of a coating layer of the electrode of the capacitor maybe exposed and contained in the printed circuit board to thereby makethe electrode exposed from the coating layer electrically connectable.In this case, it is preferable that the metal exposed from the coatinglayer mainly consists of copper. This is because high connectioncharacteristics can be ensured and connection resistance can be reducedeven if a metal layer is formed by plating on the exposed metal.

A chip capacitor having electrodes formed inside of an outer edgethereof may be employed. Due to this, even if continuity is establishedthrough the via hole, a large external electrode can be provided and theallowable range of alignment is widened, so that connection defect canbe eliminated.

A capacitor having electrodes formed in a matrix may be employed. Due tothis, a large chip capacitor can be contained in the core substrate.Accordingly, capacitance can be increased and electrical problems canbe, therefore, solved. Besides, even if going through various heathistories, the printed circuit board does not warp so easily.

A plurality of chip capacitors for providing many capacitors may becoupled to be employed as the capacitor. By doing so, it is possible toappropriately adjust capacitance and to appropriately operate the ICchip.

A resin may be filled between the core substrate and the capacitor, andthe coefficient of thermal expansion of the resin is set lower than thatof the core substrate, i.e., set closer to that of the capacitor made ofceramic. Due to this, even if an internal stress resulting from thedifference in the coefficient of thermal expansion between the coresubstrate and the capacitor occurs in a heat cycle test, cracks,separation and the like less occur to the core substrate, thereby makingit possible to attain high reliability.

A printed circuit board manufacturing method may be characterized bycomprising at least the following steps (a) to (e):

(a) embedding a capacitor in a core substrate;(b) forming a resin insulating layer on an upper surface of saidcapacitor;(c) forming a relatively large lower-layer via hole connected to anelectrode of said capacitor, in said resin insulating layer;(d) forming an interlayer resin insulating layer on an upper surface ofsaid core substrate; and(e) providing a plurality of relatively small upper-layer via holesconnected to one said lower-layer via hole, in said interlayer resininsulating layer.

A capacitor may be included in the core substrate, a relatively largelower-layer via hole connected to a terminal of the capacitor is formed,and a plurality of relatively small upper-layer via holes connected toone the lower-layer via hole are provided in an interlayer resininsulating layer on an upper surface of the core substrate. By doing so,it is possible to connect the terminal of the capacitor to thelower-layer via even if the position at which the capacitor is providedis shifted, and it is possible to ensure the supply of power from thecapacitor to the IC chip. Further, by providing a plurality ofrelatively small upper-layer via holes, it is possible to obtain thesame effect as that of connecting inductances in parallel. Thus, thehigh frequency characteristics of power supply lines and ground linesare enhanced, thereby making it possible to prevent the malfunction ofthe IC chip due to lack of supply of power or the variation of earthlevel. Moreover, since the wiring length can be shortened, it ispossible to reduce loop inductance.

One capacitor may be contained in a concave portion formed in the coresubstrate. Thus, the capacitor is arranged in the core substrate, sothat the distance between the IC chip and the capacitor is shortened andit is possible to reduce the loop inductance of the printed circuitboard.

A plurality of capacitors may be contained in the concave portion. Dueto this, it is possible to realize the high integration of capacitors.

A through hole may be formed in a resin material containing a resinserving as a core material, and a resin material is bonded to the resinmaterial in which the through hole is formed, thereby forming a coresubstrate having a concave portion. Due to this, it is possible to forma core substrate having a concave portion which has a flat base.

A filled via hole having a flat surface may be employed as thelower-layer via hole. Due to this, it is possible to directly connect aplurality of upper-layer via holes to one lower-layer via hole. Thus, itis possible to enhance the characteristics of the connection between thelower-layer via hole and the upper-layer via hole and to thereby ensurethe supply of power from the capacitor to the IC chip.

Upper surfaces of the plurality of capacitors within the concave portionmay be pressed or struck from above, thereby making heights of the uppersurfaces of the capacitors uniform. Accordingly, in providing aplurality of capacitors within the concave portion, the heights of thecapacitors can be made uniform and the core substrate can be made smootheven if the sizes of the plural capacitors are uneven. Thus, it ispossible to appropriately form upper interlayer resin insulating layersand conductor circuits without hampering the smoothness of the coresubstrate, and, therefore, to decrease the probability of the occurrenceof defective printed circuit boards.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram showing a process for manufacturing a printedcircuit board according to the first embodiment of the presentinvention;

FIG. 2 is a diagram showing a process for manufacturing the printedcircuit board according to the first embodiment of the presentinvention;

FIG. 3 is a diagram showing a process for manufacturing the printedcircuit board according to the first embodiment of the presentinvention;

FIG. 4 is a diagram showing a process for manufacturing the printedcircuit board according to the first embodiment of the presentinvention;

FIG. 5 is a diagram showing a process for manufacturing the printedcircuit board according to the first embodiment of the presentinvention;

FIG. 6 is a diagram showing a process for manufacturing the printedcircuit board according to the first embodiment of the presentinvention;

FIG. 7 is a cross-sectional view of the printed circuit board accordingto the first embodiment of the present invention;

FIG. 8 is a cross-sectional view showing a state in which an IC chip ismounted on the printed circuit board shown in FIG. 7 and that theprinted circuit board is attached to a daughter board;

FIG. 9 is a cross-sectional view showing a state in which an IC chip ismounted on a printed circuit board according to the first other exampleof the first embodiment according to the present invention;

FIG. 10 is a diagram showing a process for manufacturing a printedcircuit board according to the first modification of the firstembodiment of the present invention;

FIG. 11 is a cross-sectional view of the printed circuit board accordingto the first modification of the first embodiment of the presentinvention;

FIG. 12 is a graph showing the change of the voltage supplied to the ICchip relative to time;

FIG. 13 is a cross-sectional view of a chip capacitor contained in theprinted circuit board according to the first modification of the firstembodiment;

FIG. 14 is a plan view of chip capacitors contained in a printed circuitboard according to the second modification of the first embodiment;

FIG. 15 is a plan view of a chip capacitor contained in the printedcircuit board according to the second modification of the firstembodiment;

FIG. 16 is a plan view of chip capacitors contained in the printedcircuit board according to the second modification of the firstembodiment;

FIG. 17 is a view showing a process for manufacturing a printed circuitboard according to the second embodiment of the present invention;

FIG. 18 is a view showing a process for manufacturing the printedcircuit board according to the second embodiment of the presentinvention;

FIG. 19 is a cross-sectional view of the printed circuit board accordingto the second embodiment of the present invention;

FIG. 20 is a cross-sectional view showing a state in which an IC chip ismounted on the printed circuit board shown in FIG. 19 and that theprinted circuit board is attached to a daughter board;

FIG. 21 is a view showing a process for manufacturing the printedcircuit board according to the second embodiment of the presentinvention;

FIG. 22 is a view showing a process for manufacturing the printedcircuit board according to the second embodiment of the presentinvention;

FIG. 23 is a cross-sectional view showing a state in which an IC chip ismounted on the printed circuit board according to the second embodimentof the present invention;

FIG. 24 is a cross-sectional view showing a state in which an IC chip ismounted on a printed circuit board according to a modification of thesecond embodiment of the present invention;

FIG. 25 is a view showing a process for manufacturing a printed circuitboard according to the third embodiment of the present invention;

FIG. 26 is a view showing a process for manufacturing the printedcircuit board according to the third embodiment of the presentinvention;

FIG. 27 is a view showing a process for manufacturing the printedcircuit board according to the third embodiment of the presentinvention;

FIG. 28 is a view showing a process for manufacturing the printedcircuit board according to the third embodiment of the presentinvention;

FIG. 29 is a view showing a process for manufacturing the printedcircuit board according to the third embodiment of the presentinvention;

FIG. 30 is a cross-sectional view of the printed circuit board accordingto the third embodiment of the present invention;

FIG. 31 is a cross-sectional view showing a state in which an IC chip ismounted on the printed circuit board shown in FIG. 30 and that theprinted circuit board is attached to a daughter board;

FIG. 32 is a cross-sectional view showing a state in which an IC chip ismounted on a printed circuit board according to a modification of thethird embodiment of the present invention;

FIG. 33 is a view showing a process for manufacturing a printed circuitboard according to the first modification of the third embodiment of thepresent invention;

FIG. 34 is a view showing a process for manufacturing the printedcircuit board according to the first modification of the thirdembodiment of the present invention;

FIG. 35 is a view showing a process for manufacturing the printedcircuit board according to the first modification of the thirdembodiment of the present invention;

FIG. 36 is a cross-sectional view of the printed circuit board accordingto the first modification of the third embodiment of the presentinvention;

FIG. 37 is a view showing a process for manufacturing a printed circuitboard according to the fourth embodiment of the present invention;

FIG. 38 is a view showing a process for manufacturing the printedcircuit board according to the fourth embodiment of the presentinvention;

FIG. 39 is a view showing a process for manufacturing the printedcircuit board according to the fourth embodiment of the presentinvention;

FIG. 40 is a view showing a process for manufacturing the printedcircuit board according to the fourth embodiment of the presentinvention;

FIG. 41 is a view showing a process for manufacturing the printedcircuit board according to the fourth embodiment of the presentinvention;

FIG. 42 is a cross-sectional view of the printed circuit board accordingto the fourth embodiment of the present invention;

FIG. 43 is a cross-sectional view showing a state in which an IC chip ismounted on the printed circuit board according to the fourth embodimentof the present invention;

FIG. 44(A) is an enlarged view of a via hole 660 shown in FIG. 42 andFIG. 44(B) is a view seen from an arrow B of FIG. 44(A);

FIG. 45 is a view showing a process for manufacturing a printed circuitboard according to the first modification of the fourth embodiment ofthe present invention;

FIG. 46 is a view showing a process for manufacturing the printedcircuit board according to the first modification of the fourthembodiment of the present invention;

FIG. 47 is a view showing a process for manufacturing the printedcircuit board according to the first modification of the fourthembodiment of the present invention;

FIG. 48 is a view showing a process for manufacturing the printedcircuit board according to the first modification of the fourthembodiment of the present invention;

FIG. 49 is a view showing a process for manufacturing the printedcircuit board according to the first modification of the fourthembodiment of the present invention;

FIG. 50 is a view showing a process for manufacturing the printedcircuit board according to the first modification of the fourthembodiment of the present invention;

FIG. 51 is a view showing a process for manufacturing the printedcircuit board according to the first modification of the fourthembodiment of the present invention;

FIG. 52 is a cross-sectional view showing a state in which an IC chip ismounted on the printed circuit board according to the first modificationof the fourth embodiment of the present invention; and

FIG. 53 is a cross-sectional view showing a state in which an IC chip ismounted on the printed circuit board according to the secondmodification of the fourth embodiment of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION First Embodiment

The embodiments of the present invention will be described hereinafterwith reference to the accompanying drawings.

First, the constitution of a printed circuit board according to thefirst embodiment of the present invention will be described withreference to FIGS. 7 and 8. FIG. 7 is a cross-sectional view of aprinted circuit board 10 and FIG. 8 shows a state in which an IC chip 90is mounted on the printed circuit board 10 shown in FIG. 7 and that theprinted circuit board 10 is attached to a daughter board 95.

As shown in FIG. 7, the printed circuit board 10 consists of a coresubstrate 30 containing a plurality of chip capacitors 20 and buildupwiring layers 80A and 80B. Each of the buildup wiring layers 80A and 80Bconsists of a resin layer 40 and interlayer resin insulating layers 140and 141. Conductor circuits 58 and via holes 60 are formed on the upperresin layer 40. Conductor circuits 158 and via holes 160 are formed oneach of the upper and lower interlayer resin insulating layers 140.Conductor circuit 159 and via holes 164 are formed on each of the upperand lower interlayer resin insulating layers 141. Solder resist layers70 are formed on the interlayer resin insulating layers 141,respectively. The buildup wiring layers 80A and 80B are connected toeach other byway of through holes 56 formed in the core substrate 30.

Each of the chip capacitors 20 consists of the first electrode 21, thesecond electrode 22 and a dielectric 23 put between the first and secondelectrodes as shown in FIG. 7. A plurality of pairs of first conductivefilms 24 connected to the first electrode 21 side and second conductivefilms 25 connected to the second electrode 22 side are arranged on thedielectric 23 to face one another.

As shown in FIG. 8, solder bumps 76U to be connected to the pads 92P1and 92P2 of the IC chip 90 are formed on the upper buildup wiring layer80A. Solder bumps 76D to be connected to the pads 94P1 and 94P2 of thedaughter board 95 are formed on the lower buildup wiring layer 80B.

The grounding pad 92P1 of the IC chip 90 is connected to the firstelectrode 21 of the corresponding chip capacitor 20 through the bump76U—the conductor circuit 159—the via hole 164—the conductor circuit158—the via hole 160—the conductor circuit 58—the via hole 60. Thegrounding pad 94P1 of the daughter board 95 is connected to the firstelectrode 21 of the corresponding chip capacitor 20 through the bump76D—the via hole 164—the conductor circuit 158—the via hole 160—thethrough hole 56—the conductor circuit 58—the via hole 60.

The power supply pad 92P2 of the IC chip 90 is connected to the secondelectrode 22 of the corresponding chip capacitor 20 through the bump76U—the via hole 164—the conductor circuit 158—the via hole 160—theconductor circuit 158—the via hole 60. The power supply pad 94P2 of thedaughter board 95 is connected to the second electrode 22 of thecorresponding chip capacitor 20 through the bump 76D—the via hole164—the conductor circuit 158—the via hole 160—the through hole 56—thevia hole 60. Signal pads of the IC chip are, though not shown, connectedto signal pads of the daughter board through the conductor circuits ofthe printed circuit board, the via holes and the through holes,respectively.

As shown in FIG. 7, the core substrate 30 in this embodiment consists ofthe first resin substrate 30 a having conductive pad sections 34 forconnecting the chip capacitors 20 formed on one side, the second resinsubstrate 30 b connected to the first resin substrate 30 a through abonding resin layer (bonding plate) 38 a and the third resin substrate30 c connected to the second resin substrate 30 b through a bondingresin layer (bonding plate) 38 b. An opening 30B capable of containingthe chip capacitors 20 is formed in the second resin substrate 30 b.

By forming the opening, the chip capacitors 20 can be contained in thecore substrate 30. Due to this, the distance between the IC chip 90 andthe chip capacitors 20 is shortened to thereby reduce the loopinductance of the printed circuit board 10. Besides, since the firstresin substrate 30 a, the second resin substrate 30 b and the thirdresin substrate 30 c are provided in a laminated manner, the coresubstrate 30 can obtain sufficient strength. Further, since the coresubstrate 30 is constituted smoothly by providing the first substrate 30a and the third substrate 30 c on the both sides of the core substrate30, respectively, the resin layers 40, 140 and 141 and the conductorcircuits 58, 158 and 159 can be formed on the core substrate 30appropriately and the probability of the occurrence of defective printedcircuit boards can be thereby decreased.

Moreover, in this embodiment, as shown in FIG. 1(D), an insulatingbonding agent 33 is interposed between the first resin substrate 30 aand each chip capacitor 20. Here, the coefficient of the thermalexpansion of the bonding agent 33 is set lower than that of the coresubstrate 30, i.e., set close to that of the chip capacitors 20 made ofceramic. Due to this, even if an internal stress resulting from thedifference in the coefficient of thermal expansion among the coresubstrate, the bonding layers 40 and the chip capacitors 20, occurs in aheat cycle test, cracks, separation and the like less occur to the coresubstrate, making it possible to attain high reliability. It is alsopossible to prevent the occurrence of migration.

A method of manufacturing the printed circuit board described above withreference to FIG. 7 will be described with reference to FIGS. 1 to 7.

(1) A copper-clad laminated plate having a copper foil 32 laminated onone side of the first resin substrate 30 a having a core having athickness of 0.1 mm and made of glass cloth or the like which a BT(Bismaleimide-Triazine) resin is impregnated into and hardened in, isemployed as a starting material (FIG. 1(A)).

Next, the copper foil 32 side of the copper-clad laminated plate isetched into a pattern, thereby forming conductive pad sections 34 on oneside of the first resin substrate 30 a (FIG. 1(B)).

It is noted that a substrate made of ceramic or AIN cannot be used asthe core substrate. This is because such a substrate has poorworkability for the outside shape thereof, sometimes cannot containcapacitors and has gaps even if filled with a resin.

(2) Then, using a printer, an bonding material 36 such as a solder pasteor a conductive paste is applied onto the conductive pad sections 34(FIG. 1(C)). The pad sections 34 may be subjected to potting in additionto the application of the bonding material. As the solder paste, one ofSn/Pb, Sn/Sb, Sn/Ag and Sn/Ag/Cu can be employed. Then, resin filler 33is provided between the conductive pads 34 (FIG. 1(D)). By doing so, itis possible to fill the gaps between chip capacitors 20 and the firstresin substrate 30 a to be described later. Next, a plurality of chipcapacitors 20 made of ceramic are disposed on the conductive padsections 34 and connected to the conductive pad sections 34 through thebonding material 36 (FIG. 2(A)). Either one or a plurality of chipcapacitors 20 may be employed; however, if a plurality of chipcapacitors 20 are employed, the high integration of capacitors can berealized.(3) Next, resin layers for bonding (bonding resin layers) 38 a and 38 beach having a core made of glass cloth or the like and impregnated withan epoxy resin as well as the second resin substrate 30 b (having athickness of 0.4 mm) and the third resin substrate 30 c (having athickness of 0.1 mm) each having a core made of glass cloth or the likewhich a BT resin is impregnated into and hardened in, are prepared.Through holes 38A and 30B capable of containing the chip capacitors 20are formed in the bonding resin layer 38 a and the second resinsubstrate 30 b, respectively. First, the second resin substrate 30 b ismounted on the third resin substrate 30 c through the bonding resinlayer 38 b. Next, the first resin substrate 30 a is inverted and mountedon the second resin substrate 30 b through the bonding resin layer 38 a.Namely, the first resin substrate 30 a is superposed on the second resinsubstrate 30 b so that the chip capacitors 20 connected to the firstresin substrate 30 a can be directed toward the bonding resin layer 38 aside and can be contained in the through holes formed in the secondresin substrate 30 b (FIG. 2(B)). By doing so, the chip capacitors 20can be contained in the core substrate 30 and the printed circuit boardhaving reduced loop inductance can be provided.(4) The superposed substrates are pressurized using a thermal press,thereby integrating the first, second and third resin substrates 30 a,30 b and 30 c in a multilayer manner and forming the core substrate 30having a plurality of chip capacitors 20 (FIG. 2(C)). First, bypressurizing the substrates, the epoxy resin (insulating resin) ispushed outside of the bonding resin layers 38 a and 38 b and the gapsbetween the opening 30B and the chip capacitors 20 are filled with theresin. Further, since the substrates are pressurized and, at the sametime, heated, the epoxy resin is hardened and the first resin substrate30 a, the second resin substrate 30 b and the third resin substrate 30 care fixedly bonded to one another by interposing the bonding resinlayers 38 a and 38 b as bonding resin. In this embodiment, the gapswithin the opening 30B are filled with the epoxy resin flowing out ofthe bonding resin layers. Alternatively, filler can be provided in theopening 30B.

Since the both sides of the core substrate 30 are the first resinsubstrate 30 a and the third resin substrate 30 c which are smooth,respectively, the resin layer 40 and the conductor circuits 58 can beappropriately formed in steps to be described later without damaging thesmoothness of the core substrate 30 and the probability of theoccurrence of defective printed circuit boards can be decreased.Further, the core substrate 30 can obtain sufficient strength.

(5) Thermosetting epoxy resin sheets to be described later are laminatedby vacuum pressing onto the substrate 30 which has been subjected to theabove-stated steps, at a pressure of 5 kg/cm² while raising temperatureto 50 to 150° C. to thereby provide interlayer resin insulating layers40 (FIG. 2(D)). The degree of vacuum during vacuum pressing is 10 mmHg.(6) Next, openings 42 for via holes reaching the conductive pad sections34 are formed in the interlayer resin insulating layer 40 at the firstresin substrate 30 a side and the first resin substrate 30 a by applyinglaser (FIG. 3(A)).(7) Then, penetrating holes 44 for through holes are formed in the coresubstrate 30 by drilling or applying laser (FIG. 3(B)). Thereafter, ade-smear process is performed using oxygen plasma. Alternatively, ade-smear process using chemicals such as permanganate may be performed.(8) Using SV-4540 manufactured by ULVAC JAPAN, Ltd., a plasma process isperformed to form rough surfaces 46 on the entire surfaces of the coresubstrate 30. The plasma process is performed for two minutes whileusing, as inert gas, argon gas on conditions of power of 200 W, a gaspressure of 0.6 Pa and a temperature of 70° C. Then, sputtering isperformed with Ni and Cu as targets and Ni—Cu metal layers 48 are formedon the surfaces of the interlayer resin insulating layers 40,respectively (FIG. 3(C)). While sputtering is employed herein, metallayers of copper, nickel or the like may be formed by electrolessplating. In some cases, after performing sputtering, electroless platedfilms may be formed. A roughing process may be performed using an acidor an oxidizer. The rough layers are preferably 0.1 to 5 μm thick.(9) Next, photosensitive dry films are bonded to the surfaces of theNi—Cu metal layers 48 and exposure and development processes areperformed while mounting masks, thereby forming resists 50 each having apredetermined pattern (FIG. 3(D)). The core substrate 30 is immersed inan electroplating solution, current is applied to the core substrate 30through the Ni—Cu metal layers 48 and electroplating is conducted toportions in which the resists 50 are not formed on the followingconditions, thereby forming electroplated films 52 (FIG. 4(A)).

[Electroplating Solution]

Sulfuric acid 2.24 mol/l Copper sulfate 0.26 mol/l Additive (KaparacidHL 19.5 mol/l manufactured by Atotech Japan

[Electroplating Conditions]

Current density 1 A/dm² Duration 120 minutes temperature 22 ± 2° C.(10) After separating and removing the resists 50 with 5% NaOH, theNi—Cu metal layers 48 under the resists 50 are dissolved and removed byetching with a solution mixture of a nitric acid, a sulfuric acid andhydrogen peroxide, thereby forming through holes 56 and conductorcircuits 58 (including via holes 60) each consisting of the Ni—Cu metallayer 48 and the electroplated film 52 and having a thickness of 16 μm.After washing and drying the resultant substrate, an etching solution issprayed on the both sides of the substrate and the surfaces of thethrough holes 56 and the conductor circuits 58 (including the via holes60) are etched, thereby forming rough layers 62 on the entire surfacesof the through holes 56 and the conductor circuits 58 (including the viaholes 60) (FIG. 4(B)). As the etching solution, a mixture of 10 parts byweight of an imidazole copper (II) complex, 7 parts by weight of aglycolic acid, 5 parts by weight of potassium chloride and 78 parts byweight of ion-exchange water is employed.(11) Resin filler 64 mainly consisting of an epoxy resin is filled inthe through holes 56, and heated and dried (FIG. 4(C)).

(12) Then, the thermosetting epoxy resin sheets used in the step of (5)are laminated on the substrate by vacuum pressing at a pressure of 5kg/cm² while raising temperature to 50 to 150° C., thereby providinginterlayer resin insulating layers 140 (FIG. 4(D). The degree of vacuumduring vacuum pressing is 10 mmHg.

(13) Openings 142 for via holes are then formed in the interlayer resininsulating layers 140 by applying laser (FIG. 5(A)).(14) Thereafter, by repeating the steps of (8) to (10), conductorcircuits 158 (including via holes 160) each consisting of the Ni—Cumetal layer 148 and the electroplated film 152 and having a thickness of16 μm, and rough surfaces 158 a are formed on each of the interlayerresin insulating layers 140 (FIG. 5(B)).(15) By further repeating the steps of (12) to (14), interlayer resininsulating layers 141, conductor circuits 159 (including via holes 164)and rough surfaces 159 a are formed further above (FIG. 5(C)).(16) Next, 46.67 parts by weight of oligomer (having a molecular weightof 4000) which is obtained by forming 50% of epoxy groups of 60 wt %cresol novolac epoxy resin (manufactured by Nippon Kayaku Co., Ltd.)dissolved in diethylene glycol dimethyl ether (DMDG) into an acrylicstructure and which imparts photosensitive characteristic, 15 parts byweight of 80 wt % bisphenol A epoxy resin (Epicoat 1001 manufactured byYuka Shell) dissolved in methyl ethyl ketone, 1.6 parts by weight of animidazole hardening agent (2E4MZ-CN manufactured by Shikoku ChemicalsCorp.), 3 parts by weight of polyhydric acrylic monomer which isphotosensitive monomer (R604 manufactured by Kyoei Chemical), 1.5 partsby weight of polyhydric acrylic monomer (DPE6A manufactured by KyoeiChemical) and 0.71 parts by weight of a dispersing deforming agent (S-65manufactured by SANNOPCO) are put in a container, stirred and mixed withone another to prepare a mixture composition. Then, 2.0 parts by weightof benzophenone (manufactured by KANTO KAGAKU) serving as aphotoinitiator and 0.2 parts by weight of Michler's ketone (manufacturedby KANTO KAGAKU) serving as a photosensitizer are added to the resultantmixture, thereby obtaining a solder resist composition (organic resininsulating material) having a viscosity adjusted to 2.0 Pa·s at 25° C.

The viscosity is measured by a B-type viscometer (DVL-B typemanufactured by Tokyo Keiki Co., Ltd.) with a rotor No. 4 for 60 rpm anda rotor No. 3 for 4.6 rpm.

(17) Next, the said solder resist composition is applied to each side ofthe substrate 30 to have a thickness of 20 μm and dried at 70° C. for 20minutes and 70° C. for 30 minutes. Thereafter, while photomasks each ofwhich has a thickness of 5 mm and on which the pattern of solder resistopening portions are drawn, are made hermetic contact with the solderresist layers 70, respectively, exposed to ultraviolet rays of 1000mJ/cm², developed with a DMTG solution, thereby forming openings 71U and71D (FIG. 6(A)).(18) Then, the substrate on which the solder resist layers (organicresin insulating layers) 70 have been formed are immersed in anelectroless nickel plating solution containing nickel chloride (2.3×10⁻¹mol/l), sodium hypophosphite (2.8×10⁻¹ mol/l) and sodium citrate(1.6×10⁻¹ mol/l) and having a pH of 4.5 for 20 minutes to form nickelplated layers 72 each having a thickness of 5 μm, on the openingportions 71U and 71D, respectively. Further, the substrate is immersedin an electroless plating solution containing potassium gold cyanide(7.6×10⁻³ mol/l), ammonium chloride (1.9×10⁻¹ mol/l), sodium citrate(1.2×10⁻¹ mol/l) and sodium hypophosphite (1.7×10⁻¹ mol/l) on conditionsof 80° C. for 7.5 minutes to form gold plated layers 74 each having athickness of 0.03 μm, on the nickel plated layers 72, respectively (FIG.6(B)).(19) Thereafter, a solder paste is printed on each of the openings 71Uand 71D of the solder resist layers 70 and a reflow process is conductedat 200° C., thereby forming solder bumps (solder bodies) 76U and 76D.Consequently, it is possible to obtain the printed circuit board 10having the solder bumps 76U and 76D (FIG. 7).

Next, description will be given to the mounting of the IC chip 90 on theprinted circuit board 10 completed through the above-stated steps and tothe attachment of the printed circuit board 10 to the daughter board 95,with reference to FIG. 8. The IC chip 90 is mounted on the printedcircuit board 10 thus completed so that the solder pads 92P1 and 92P2 ofthe IC chip 90 correspond to the solder bumps 76U of the printed circuitboard 10 and a reflow process is performed, thereby attaching the ICchip 90 to the printed circuit board 10. Likewise, a reflow process isperformed so that the pads 94P1 and 94P2 of the daughter board 95correspond to the solder bumps 76D of the printed circuit board 10,thereby attaching the printed circuit board 10 to the daughter board 95.

The above-stated resin films contain a refractory resin, solubleparticles, a hardening agent and other components, each of which will bedescribed hereinafter.

The resin films employed in the manufacturing method of the presentinvention has particles soluble in an acid or an oxidizer (to bereferred to as “soluble particles” hereinafter) which particles aredispersed in a resin refractory to the acid or the oxidizer (to bereferred to as “refractory resin” hereinafter).

The expressions “refractory” and “soluble” will now be described. Whenmaterials are immersed in solution composed of the same acid or the sameoxidizers for the same time, a material of a type which is dissolved ata relatively high dissolving rate is called a “soluble” material forconvenience. A material of a type which is dissolved at a relativelyslow dissolving rate is called a “refractory material” for convenience.

The soluble particles are exemplified by resin particles which aresoluble in acid or an oxidizer (hereinafter called “soluble resinparticles”), inorganic particles which are soluble in acid or anoxidizer (hereinafter called “inorganic soluble particles”) and metalparticles which are soluble in acid or an oxidizer (hereinafter called“soluble metal particles”). The foregoing soluble particles may beemployed solely or two or more particles may be employed.

The shape of each of the soluble particles is not limited. The shape maybe a spherical shape or a pulverized shape. It is preferable that theparticles have a uniform shape. The reason for this lies in that a roughsurface having uniformly rough pits and projections can be formed.

It is preferable that the mean particle size of the soluble particles is0.1 μm to 10 μm. When the particles have the diameters satisfying theforegoing range, particles having two or more particle sizes may beemployed. That is, soluble particles having a mean particle size of 0.1μm to 0.5 μm and soluble particles having a mean particle size of 1 μmto 3 μmm may be mixed. Thus, a more complicated rough surface can beformed. Moreover, the adhesiveness with the conductor circuit can beimproved. In the present invention, the particle size of the solubleparticles is the length of a longest portion of each of the solubleparticles.

The soluble resin particles may be particles constituted bythermosetting resin or thermoplastic resin. When the particles areimmersed in solution composed of acid or an oxidizer, the particles mustexhibit dissolving rate higher than that of the foregoing refractoryresin.

Specifically, the soluble resin particles are exemplified by particlesconstituted by epoxy resin, phenol resin, phenoxy resin, polyimideresin, polyphenylene resin, polyolefin resin or fluorine resin. Theforegoing material may be employed solely or two or more materials maybe mixed.

The soluble resin particles may be resin particles constituted byrubber. Rubber above is exemplified by polybutadiene rubber, a varietyof denatured polybutadiene rubber, such as denatured epoxy rubber,denatured urethane rubber or denatured (metha) acrylonitrile rubber, and(metha) acrylonitrile butadiene rubber containing a carboxylic group.When the foregoing rubber material is employed, the soluble resinparticles can easily be dissolved in acid or an oxidizer. That is, whenthe soluble resin particles are dissolved with acid, dissolution ispermitted with acid except for strong acid. When the soluble resinparticles are dissolved, dissolution is permitted with permanganatewhich has a relatively weak oxidizing power. When chromic acid isemployed, dissolution is permitted even at a low concentration.Therefore, retention of the acid or the oxidizer on the surface of theresin can be prevented. When a catalyst, such as palladium chloride, issupplied after the rough surface has been formed as described later,inhibition of supply of the catalyst and oxidation of the catalyst canbe prevented.

The inorganic soluble particles are exemplified by particles made of atleast a material selected from a group consisting of an aluminumcompound, a calcium compound, a potassium compound, a magnesium compoundand a silicon compound.

The aluminum compound is exemplified by alumina and aluminum hydroxide.The calcium compound is exemplified by calcium carbonate and calciumhydroxide. The potassium compound is exemplified by potassium carbonate.The magnesium compound is exemplified by magnesia, dolomite and basicmagnesium carbonate. The silicon compound is exemplified by silica andzeolite. The foregoing material may be employed solely or two or morematerials may be mixed.

The soluble metal particles are exemplified by particles constituted byat least one material selected from a group consisting of copper,nickel, iron, zinc, lead, gold, silver, aluminum, magnesium, potassiumand silicon. The soluble metal particles may have surfaces coated withresin or the like in order to maintain an insulating characteristic.

When two or more types of the soluble particles are mixed, it ispreferable that the combination of the two types of soluble particles iscombination of resin particles and inorganic particles. Since each ofthe particles has low conductivity, an insulating characteristic withthe resin film can be maintained. Moreover, the thermal expansion caneasily be adjusted with the refractory resin. Thus, occurrence of acrack of the interlayer resin insulating layer constituted by the resinfilm can be prevented. Thus, separation between the interlayer resininsulating layer and the conductor circuit can be prevented.

The refractory resin is not limited when the resin is able to maintainthe shape of the rough surface when the rough surface is formed on theinterlayer resin insulating layer by using acid or oxidizer. Therefractory resin is exemplified by thermosetting resin, thermoplasticresin and their composite material. As an alternative to this, theforegoing photosensitive resin of a type having photosensitivecharacteristic imparted thereto may be employed. When the photosensitiveresin is employed, exposure and development processes of the interlayerresin insulating layers can be performed to form the openings for thevia.

In particular, it is preferable that the resin containing thermosettingresin is employed. In the foregoing case, the shape of the rough surfacecan be maintained against plating solution and when a variety of heatingprocesses are performed.

The refractory resin is exemplified by epoxy resin, phenol resin,phenoxy resin, polyimide resin, polyphenylene resin, polyolefin resinand fluorine resin. The foregoing material may be employed solely or twoor more types of the materials may be mixed.

It is preferable that epoxy resin having two or more epoxy groups in onemolecule thereof is employed. The reason for this lies in that theforegoing rough surface can be formed. Moreover, excellent heatresistance and the like can be obtained. Thus, concentration of stressonto the metal layer can be prevented even under a heat cycle condition.Thus, occurrence of separation of the metal layer can be prevented.

The epoxy resin is exemplified by cresol novolac epoxy resin,bisphenol-A epoxy resin, bisphenol-F epoxy resin, phenol novolac epoxyresin, alkylphenol novolac epoxy resin, biphenol-F epoxy resin,naphthalene epoxy resin, dicyclopentadiene epoxy resin, an epoxymaterial constituted by a condensation material of phenol and anaromatic aldehyde having a phenol hydroxyl group, triglycidylisocyanurate and alicyclic epoxy resin. The foregoing material may beemployed solely or two or more material may be mixed. Thus, excellentheat resistance can be realized.

It is preferable that the soluble particles in the resin film accordingto the present invention are substantially uniformly dispersed in therefractory resin. The reason for this lies in that a rough surfacehaving uniform pits and projections can be formed. When via and throughholes are formed in the resin film, adhesiveness with the metal layer ofthe conductor circuit can be maintained. As an alternative to this, aresin film containing soluble particles in only the surface on which therough surface is formed may be employed. Thus, the portions of the resinfilm except for the surface is not exposed to acid or the oxidizer.Therefore, the insulating characteristic between conductor circuitsthrough the interlayer resin insulating layer can reliably bemaintained.

It is preferable that the amount of the soluble particles which aredispersed in the refractory resin is 3 wt % to 40 wt % with respect tothe resin film. When the amount of mixture of the soluble particles islower than 3 wt %, the rough surface having required pits andprojections cannot be formed. When the amount is higher than 40 wt %,deep portions of the resin film are undesirably dissolved when thesoluble particles are dissolved by using acid or the oxidizer. Thus, theinsulating characteristic between the conductor circuits through theinterlayer resin insulating layer constituted by the resin film cannotbe maintained. Thus, short circuit is sometimes is caused to occur.

It is preferable that the resin film contains a hardening agent andother components as well as the refractory resin.

The hardening agent is exemplified by an imidazole hardening agent, anamine hardening agent, a guanidine hardening agent, an epoxy adduct ofeach of the foregoing hardening agents, a microcapsule of each of theforegoing hardening agents and an organic phosphine compound, such astriphenylphosphine or tetraphenyl phosphonium tetraphenyl borate.

It is preferable that the content of the hardening agent is 0.05 wt % to10 wt % with respect to the resin film. When the content is lower than0.05 wt %, the resin film cannot sufficiently be hardened. Thus,introduction of acid and the oxidizer into the resin film occursgreatly. In the foregoing case, the insulating characteristic of theresin film sometimes deteriorates. When the content is higher than 10 wt%, an excessively large quantity of the hardening agent componentsometimes denatures the composition of the resin. In the foregoing case,the reliability sometimes deteriorates.

The other components are exemplified by an inorganic compound which doesnot exert an influence on the formation of the rough surface and afiller constituted by resin. The inorganic compound is exemplified bysilica, alumina and dolomite. The resin is exemplified by polyimideresin, polyacrylic resin, polyamideimide resin, polyphenylene resin,melanine resin and olefin resin. When any one of the foregoing fillersis contained, conformity of the thermal expansion coefficients can beestablished. Moreover, heat resistance and chemical resistance can beimproved. As a result, the performance of the printed circuit board canbe improved.

The resin film may contain solvent. The solvent is exemplified byketone, such as acetone, methylethylketone or cyclohexane; aromatichydrocarbon, such as ethyl acetate, butyl acetate, cellosolve acetate,toluene or xylene. The foregoing material may be employed solely or twoor more materials may be mixed.

First Other Example of First Embodiment

A printed circuit board according to the first other example of thefirst embodiment of the present invention will be described hereinafterwith reference to FIG. 9. The printed circuit board in the first otherexample of the first embodiment is almost the same as the printedcircuit board in the first embodiment stated above. However, in theprinted circuit board in the first other example, conductive connectionpins 96 are provided at the printed circuit board and the printedcircuit is connected to a daughter board through the conductiveconnection pins 96.

Further, in the first embodiment stated above, only the chip capacitors20 contained in the core substrate 30 are provided. In this example,mass storage chip capacitors 86 are mounted on the front and reversesides of the substrate.

The IC chip momentarily consumes high power and performs complexarithmetic operation. In the first other example, to supply high powerto the IC chip, chip capacitors 20 and chip capacitors 86 for powersupply are provided. The advantage derived from these chip capacitorswill be described with reference to FIG. 12.

FIG. 12 is a graph with a vertical axis indicating voltage supplied tothe IC chip and a horizontal axis indicating time. In FIG. 12, two-dotchain line C denotes the voltage variation of a printed circuit boardwhich is not provided with power supply capacitors. If power supplycapacitors are not provided, voltage attenuates greatly. A broken line Adenotes the voltage variation of a printed circuit board having chipcapacitors mounted on the surfaces thereof. Compared with the two-dotchain line C, voltage does not drop greatly. However, since loop lengthis larger, rate-controlled power supply cannot be conductedsufficiently. Namely, at the start of the supply of power, voltagefalls. Further, a two-dot chain line B denotes the voltage drop of aprinted circuit board including the chip capacitors described above withreference to FIG. 8. In this case, loop length can be shortened;however, mass storage chip capacitors cannot be contained in a coresubstrate 30 and voltage, therefore, varies. Here, a solid line Edenotes the voltage variation of the printed circuit board in the firstother example which printed circuit board has the chip capacitors 20mounted in the core substrate and the mass storage chip capacitors 86mounted on the surfaces thereof. Voltage variation is minimized byproviding the chip capacitors 20 and the mass storage chip capacitors 86(having relatively high inductance) in the vicinity of the IC chip.

First Modification of First Embodiment

Next, a printed circuit board according to the first modification of thefirst embodiment of the present invention will be described withreference to FIG. 11.

The printed circuit board in the first modification is almost the samein constitution as the printed circuit board in the above-stated firstembodiment. However, in the printed circuit board 14 in the firstmodification, conductor circuits 35 are formed on one sides of the firstresin substrate 30 a and the third resin substrate 30 c, and conductorcircuits 37 are formed on the both sides of the second resin substrate30 b provided with an opening 30B for containing chip capacitors 20. Inthe first embodiment, the conductor circuits 35 are formed on one sidesof the first resin substrate 30 a and the third resin substrate 30 c andthe conductor circuits 37 are formed on the both sides of the secondresin substrate 30 b. Due to this, it is possible to advantageouslyincrease wiring density and advantageously reduce the number ofinterlayer resin insulating layers to be built up.

Furthermore, as shown in FIG. 13(A), in the chip capacitor 20 of theprinted circuit board in the first modification, after the coating layer(not shown) of the first and second electrodes 21 and 22 are completelyseparated, the first and second electrodes 21 and 22 are coated withcopper plated films 29. The first and second electrodes 21 and 22 eachcoated with the copper plated film 29 are electrically connected to eachother by a via hole 50 made of a copper plated material. Here, theelectrodes 21 and 22 of the chip capacitor are made by metalization andhave irregularities on the surfaces thereof. In the first modification,since the surfaces of the first and second electrodes 21 and 22 aresmoothed by the copper plated films 29, no migration occurs to therebycause no disadvantage to the electrodes of the capacitor.

The copper plated films 29 are provided after the nickel/tin layer(coating layer) coated on the surface of each metal layer 26 in a phaseof manufacturing chip capacitors 20 is separated in a phase of mountingthe chip capacitors on the printed circuit board. Alternatively, thecopper plated films 29 can be directly coated on the metal layers 26 inthe phase of manufacturing the chip capacitors 20. Namely, in the firstmodification, as in the case of the first embodiment, after openingsreaching the copper plated films 29 of the electrodes are provided byapplying laser, a de-smear process is performed to thereby form viaholes by copper plating. Accordingly, even if an oxide film is formed onthe surface of the copper plated film 29, the oxide film can be removedby the laser and de-smear processes, thereby making it possible toestablish connection appropriately.

As shown in FIG. 13(B), it is also possible to employ the first andsecond electrodes 21 and 22 of the capacitor 20 while removing part ofthe coats 28 of the electrodes 21 and 22. This is because connectioncharacteristics can be enhanced by exposing the first and secondelectrodes 21 and 22.

Further, rough layers 23 a are provided on the surfaces of a dielectric23 of the chip capacitor 20 which dielectric is made of ceramic. Due tothis, the adhesiveness between the chip capacitor 20 made of ceramic andthe first resin substrate 30 a made of a resin is high and the firstresin substrate 30 a is not separated on the interface therebetween evenif a heat cycle test is conducted. The rough layers 23 a can be formedby polishing the surfaces of the chip capacitor 20 after sintering themor by roughing the surfaces before sintering them. In the firstmodification, the surfaces of the capacitor are roughed and theadhesiveness between the capacitor and the resin is thereby enhanced.Alternatively, a silane coupling process can be conducted to thesurfaces of the capacitor.

A process of manufacturing the printed circuit board according to thefirst modification of the present invention will be describedhereinafter with reference to FIGS. 10 and 11.

(1) The first resin substrate 30 a having a core having a thickness of0.1 mm and made of glass cloth or the like which a BT(Bismaleimide-Triazine) resin is impregnated into and hardened in, isprepared. Conductive pad sections 34 are formed on one side of the firstresin substrate 30 a and conductor circuits 35 are formed on the otherside of the substrate 30 a. Next, a plurality of chip capacitors 20 aremounted on the conductive pad sections 34 through an bonding agent suchas a solder or a conductive paste and connected to the conductive padsections 34 (FIG. 10(A)).(2) Next, resin layers for bonding (bonding resin layers) 38 a, 38 beach having a core made of glass cloth or the like and impregnated withan epoxy resin as well as the second resin substrate 30 b (having athickness of 0.4 mm) and the third resin substrate 30 c (having athickness of 0.1 mm) each having a core made of glass cloth or the likewhich a BT resin is impregnated into and hardened in, are prepared.Through holes 38A and 38B capable of containing the chip capacitors 20are formed in the bonding resin layer 38 a and the second resinsubstrate 30 b, respectively. Conductor circuits 37 are formed on theboth sides of the second resin substrate 30 b and conductor circuits 35are formed on one side of the third resin substrate 30 c. First, thesecond resin substrate 30 b is mounted on a surface on which theconductor circuits 35 of the third resin substrate 30 c are not formed,through the bonding resin layer 38 b. The first resin substrate 30 a isinverted and mounted on the second resin substrate 30 b through thebonding resin layer 38 a. Namely, the first resin substrate 30 a issuperposed on the second resin substrate 30 b so that the chipcapacitors 20 connected to the first resin substrate 30 a can becontained in the opening 30B formed in the second resin substrate 30 b(FIG. 10(B)).(3) The superposed substrates are pressurized using a thermal press,thereby integrating the first, second and third resin substrates 30 a,30 b and 30 c in a multilayer manner and forming the core substrate 30having a plurality of chip capacitors 20 (FIG. 10(C)). First, bypressurizing the substrates, the epoxy resin (insulating resin) ispushed outside of the bonding resin layers 38 a and 38 b and the gapsbetween the opening 30B and the chip capacitors 20 are filled with theresin. Further, since the substrates are pressurized and, at the sametime, heated, the epoxy resin is hardened and the first resin substrate30 a, the second resin substrate 30 b and the third resin substrate 30 care fixedly bonded to one another by interposing the bonding resinlayers 38 a and 38 b as bonding resin.(4) Thermosetting epoxy resin sheets are laminated by vacuum pressingonto the substrate 30 which has been subjected to the above-statedsteps, at a pressure of 5 kg/cm² while raising temperature to 50 to 150°C. to thereby provide interlayer resin insulating layers 40 (FIG.10(D)). The degree of vacuum during vacuum pressing is 10 mmHg.(5) Next, openings 42 for via holes to be connected to the conductivepad sections 34 and the conductor circuits 35 and 37 are formed on theupper and lower surfaces of the substrate 30 by applying laser (FIG.10(E)).

Later steps are the same as those of (7) to (19) in the first embodimentstated above, which description will not be, therefore, given herein.

Second Modification of First Embodiment

Next, the constitution of a printed circuit board according to thesecond modification of the first embodiment will be described withreference to FIG. 14.

The printed circuit board in the second modification is almost the samein constitution as the printed circuit board in the first embodimentstated above. They, however, differ in chip capacitors 20 contained inthe core substrate 30. FIG. 14 is a plan view of chip capacitors. FIG.14(A) shows a chip capacitor before being cut for providing a pluralityof chip capacitors. In FIG. 14(A), a dashed line denotes a cut line. Asshown in FIG. 14(B), in the printed circuit board in the firstembodiment stated above, the first electrodes 21 and the secondelectrodes 22 are provided on the edges of the chip capacitor. FIG.14(C) shows a chip capacitor before being cut for providing a pluralityof chip capacitors in the second modification. In FIG. 14(C), a dashedline denotes a cut line. In the printed circuit board in the secondmodification, as shown in the plan view of FIG. 14(D), first electrodes21 and second electrodes 22 are provided inside of the edges of the chipcapacitor.

In the printed circuit board in the second modification, the chipcapacitors 20 each having electrodes formed inside of the outer edgesthereof are employed, so that mass storage chip capacitors can beemployed.

Next, a printed circuit board according to the first other example ofthe second modification will be described with reference to FIG. 15.

FIG. 15 is a plan view of a chip capacitor 20 contained in the coresubstrate of the printed circuit board according to the first otherexample. In the first embodiment stated above, a plurality of smallstorage chip capacitors are contained in the core substrate. In thefirst other example, by contrast, a large, mass storage chip capacitor20 is contained in the core substrate. The chip capacitor 20 consists ofthe first electrodes 21, the second electrodes 22, a dielectric 23,first conductive films 24 connected to the first electrodes 21, secondconductive films 25 connected to the second electrodes 22, electrodes 27which are not connected to the first and second conductive films 24 and25, for the connection of the upper and lower surfaces of the chipcapacitor. The IC chip and the daughter board are connected to eachother through the electrodes 27.

Since the large chip capacitor 20 is employed in the printed circuitboard in the first modification, it is possible to employ a mass storagechip capacitor. Further, since the large chip capacitor 20 is employed,the printed circuit board does not warp even if a heat cycle isperformed repeatedly.

Next, a printed circuit board according to the second other example ofthe second modification will be described with reference to FIG. 16.FIG. 16(A) shows a chip capacitor before being cut for providing aplurality of chip capacitors. In FIG. 16(A), a dashed line denotes anordinary cut line. FIG. 16(B) is a plan view of the chip capacitors. Asshown in FIG. 16(B), a plurality of (or in FIG. 16(B), three) chipcapacitors for providing multiple capacitors are coupled to one anotherand employed as a large capacitor as a whole.

In the second other example, since the large chip capacitor 20 isemployed, it is possible to employ a mass storage chip capacitor.Further, since the large chip capacitor 20 is employed, the printedcircuit board does not warp even if a heat cycle is performedrepeatedly.

In the embodiment stated above, the chip capacitors are built in theprinted circuit board. Alternatively, plate-like capacitors eachconstituted by providing a conductive film on a ceramic plate may beemployed instead of the chip capacitors.

The manufacturing method in the first embodiment makes it possible tocontain the capacitors in the core substrate and to shorten the distancebetween the IC chip and the capacitors, thereby reducing the loopinductance of the printed circuit board. Further, since the printedcircuit board is constituted by providing a plurality of resin layers,the core substrate can obtain sufficient strength. Besides, the firstresin substrate and the third resin substrate are provided on the bothsides of the core substrate, respectively, thereby constituting the coresubstrate smoothly. Thus, it is possible to appropriately forminterlayer resin insulating layers and conductor circuits on the coresubstrate and to thereby decrease the probability of the occurrence ofdefective printed circuit boards.

Moreover, since the resin is filled between the core substrate and thecapacitors, a stress resulting from the capacitors or the like can bereduced even if it occurs and no migration occurs. Due to this, there isno fear that the electrodes of the capacitors are separated from theconnection sections of the via holes and dissolved. Thus, it is possibleto maintain desired performance even if a reliability test is executed.

In addition, even if the capacitors are coated with copper, it ispossible to prevent the occurrence of migration.

Second Embodiment

The constitution of a printed circuit board according to the secondembodiment of the present invention will be described hereinafter withreference to FIGS. 19 and 20. FIG. 19 is a cross-sectional view of aprinted circuit board 210. FIG. 20 shows a state in which an IC chip 290is mounted on the printed circuit board 210 shown in FIG. 19 and thatthe printed circuit board 210 is attached to a daughter board 295.

As shown in FIG. 19, the printed circuit board 210 consists of a coresubstrate 230 containing a chip capacitor 220, and buildup wiring layers280A and 280B. The buildup wiring layers 280A and 280B are connected toeach other by through holes 256. Each of the wiring layers 280A and 280Bconsists of interlayer resin insulating layers 240 and 340. At the upperbuildup wiring layer 280A side, conductor circuits 358 and via holes 260connected to the first electrode 221 and the second electrode 222 of thechip capacitor 220, respectively, are formed on the interlayer resininsulating layer 240, and conductor circuits 358 and via holes 360 areformed on the interlayer resin insulating layers 340. At the lowerbuildup wiring layer 280B side, conductor circuits 258 are formed on theinterlayer resin insulating layer 240, and conductor circuits 358 andvia holes 360 are formed on the interlayer resin insulating layer 340.Solder resist layers 270 are formed on the interlayer resin insulatinglayers 340 of the buildup wiring layers 280A and 280B, respectively.

As shown in FIG. 19, the chip capacitor 220 consists of the firstelectrode 221, the second electrode 222 and a dielectric 23 put betweenthe first and second electrodes. A plurality of pairs of firstconductive films 224 connected to the first electrode 221 side andsecond conductive film 225 connected to the second electrode 222 sideare arranged to face one another.

As shown in FIG. 20, solder bumps 276U to be connected to the pads 292E,292P and 292S of the IC chip 290 are provided on the upper buildupwiring layer 280A. Solder bumps 276D to be connected to the pads 294E,294P and 294S of the daughter board 295 are provided on the lowerbuildup wiring layer 280B.

The signal pads 292S of the IC chip 290 shown in FIG. 20 are connectedto the signal pads 294S of the daughter board 295 through the bumps276U—the conductor circuits 358—the via holes 360—the through holes256—the via holes 360—the bumps 276D, respectively.

The grounding pad 292E of the IC chip 290 is connected to the firstelectrode 221 of the chip capacitor 220 through the bump 276U—the viahole 360—the conductor circuit 258—the via hole 260. The grounding pad294E of the daughter board 295 is connected to the first electrode 221of the chip capacitor 220 through the bump 276D—the via hole 360—thethrough hole 256—the via hole 260.

The power supply pad 292P of the IC chip is connected to the secondelectrode 222 of the chip capacitor 220 through the bump 276U—the viahole 360—the conductor circuit 258—the via hole 260. The power supplypad 294P of the daughter board 295 is connected to the second electrode222 of the chip capacitor 220 through the bump 276D—the via hole 360—thethrough hole 256—the via hole 260.

As shown in FIG. 19, the core substrate 230 in this embodiment consistsof the first resin substrate 230 a, the second resin substrate 230 bconnected to the first resin substrate 230 a through a bonding resinlayer (bonding plate) 238 a and the third resin substrate 230 cconnected to the second resin substrate 230 b through a bonding resinlayer (bonding plate) 238 b. Conductor circuits 235 are formed on theboth sides of the first resin substrate 230 a, the second resinsubstrate 230 b and the third resin substrate 230 c. A concave portion334 capable of containing the chip capacitor 220 is formed in the coresubstrate 230 by spot facing and the chip capacitor 220 is contained inthe concave portion 334.

In this way, the chip capacitor 220 can be contained in the coresubstrate 230, so that the distance between the IC chip 290 and the chipcapacitor 220 becomes short and the loop inductance of the printedcircuit board 210 can be reduced. Further, since the core substrate 230is formed by providing the first, second and third resin substrates 230a, 230 b and 230 c each having the conductor circuits 235 arranged onthe both sides thereof, wiring density within the core substrate 230increases and the number of interlayer resin insulating layers can bethereby reduced.

Furthermore, as shown in FIG. 18(A), in the second embodiment, anbonding agent 236 is interposed between the lower surface of the throughhole 34 of the core substrate 230 and the chip capacitor 220, and resinfiller 233 is filled between the side surface of the through hole 237and the chip capacitor 220. Here, the coefficients of thermal expansionof the bonding agent 236 and the resin filler 233 are set lower thanthat of the core substrate 230, i.e., set close to that of the chipcapacitor 220 made of ceramic. Due to this, even if an internal stressresulting from the difference in the coefficient of thermal expansionoccurs between the core substrate 230 and the chip capacitor 220,cracks, separation and the like less occur to the core substrate 230 andhigh reliability can be, therefore, attained. It is also possible toprevent the occurrence of migration.

Next, a method of manufacturing the printed circuit board describedabove with reference to FIG. 19 will be described with reference toFIGS. 17 to 19.

(1) A copper-clad laminated plate 231M having copper foils 232 laminatedon the both sides of resin substrates 231 a each having a core having athickness of 0.3 mm and made of glass cloth or the like which a BT(Bismaleimide-Triazine) resin is impregnated into and hardened in, isemployed as a starting material (FIG. 17(A)). The copper foils 232 ofthe copper-clad laminated plate 231M are etched into a pattern fashion,thereby forming the first, second and third resin substrates 230 a, 230b and 230 c each having the conductor circuits 235 provided on the bothsides thereof (FIG. 17(B)). The second resin substrate 230 b issuperposed on the third resin substrate 230 c through the bonding resinlayer 238 b having a core made of glass cloth or the like andimpregnated with an epoxy resin. Likewise, the first resin substrate 230a is superposed on the second resin substrate 230 b through the bondingresin layer 238 a (FIG. 17(C)).

It is noted that a substrate made of ceramic or AIN cannot be used asthe core substrate. This is because such a substrate has poorworkability for the outside shape thereof, sometimes cannot contain acapacitor and has gaps even if filled with a resin.

(2) The superposed substrates are pressurized using a thermal press,thereby integrating the first, second and third resin insulatingsubstrates 230 a, 230 b and 230 c in a multi-layer manner and formingthe core substrate 230 (FIG. 17(D)). First, by pressuring thesubstrates, the epoxy resin (insulating resin) of the bonding resinlayers 238 a and 238 b is pushed outside and the epoxy resin is madehermetic contact with the first, second and third resin substrates 230a, 230 b and 230 c. Further, since the substrates are pressurized and,at the same time, heated, the epoxy resin is hardened and the firstresin substrate 230 a, the second resin substrate 230 b and the thirdresin substrate 230 c are fixedly bonded to one another by interposingthe bonding resin layers 238 a and 238 b as bonding plates.(3) Next, a concave portion 334 for containing the chip capacitor 220 isformed in the core substrate 230 by spot facing (FIG. 17(E)). While theconcave portion for containing the capacitor is provided by spot facingin this embodiment, a core substrate provided with a container sectioncan be formed by overlaying an insulating resin substrate provided withan opening on an insulating resin substrate without an opening.(4) Then, using a printer, a thermosetting or UV hardening bondingmaterial 236 is applied onto the base of the concave portion 334 (FIG.18(A)). Alternatively, potting may be conducted instead of theapplication of the bonding material.

Next, the chip capacitor 220 is mounted on the bonding material 236(FIG. 18(B)). Either one or a plurality of chip capacitors 220 may beemployed; however, if a plurality of chip capacitors 220 are employed,the high integration of capacitors can be realized.

(5) Thereafter, a thermosetting resin is filled in the concave portion334, heated and hardened to thereby form a resin layer 233 (FIG. 18(C)).As the thermosetting resin, an epoxy resin, a phenol resin, a polyimideresin and a triazine resin are preferable. Consequently, the chipcapacitor 220 within the concave portion 334 is fixed and the gapbetween the chip capacitor 220 and the wall surface of the concaveportion 334 is filled with the resin.(6) Thermosetting epoxy resin sheets to be described later are laminatedby vacuum pressing onto the substrate 230 which has been subjected tothe above-stated steps, at a pressure of 5 kg/cm² while raisingtemperature to 50 to 150° C. to thereby provide interlayer resininsulating layers 240 (FIG. 18(D)).

The degree of vacuum during vacuum pressing is 10 mmHg. Later steps arethe same as those of (7) to (9) in the first embodiment stated above,which description will not be, therefore, given herein.

Next, description will be given to the mounting of the IC chip 290 onthe printed circuit board 210 completed through the above-stated stepsand to the attachment of the printed circuit board 210 to the daughterboard 295 with reference to FIG. 20. The IC chip 290 is mounted on theprinted circuit board 210 thus completed so that the solder pads 292E,292P and 292S of the IC chip 290 correspond to the solder bumps 276U ofthe printed circuit board 210 and a reflow process is performed, therebyattaching the IC chip 290 to the printed circuit board 210. Likewise, areflow process is performed so that the pads 294E, 294P and 294S of thedaughter board 295 correspond to the solder bumps 276D of the printedcircuit board 210, thereby attaching the printed circuit board 210 tothe daughter board 295.

The thermosetting epoxy resin sheets forming the above-stated interlayerresin insulating layers 240 and 340 each contain a refractory resin,soluble particles, a hardening agent and other components, each of whichis the same as that in the first embodiment already described above andwill not be described herein.

First Modification of Second Embodiment

Next, a printed circuit board 212 according to the first modification ofthe second embodiment of the present invention will be described withreference to FIG. 23. In the second embodiment stated above, a BGA (ballgrid array) is provided. The printed circuit board in the firstmodification of the second embodiment is constituted into a PGA systemfor establishing connection through conductive connection pins 296 asshown in FIG. 23.

Further, in the second embodiment stated above, the concave portion 334for containing the chip capacitor 220 is provided in the core substrate230 by spot facing to allow the chip capacitor 220 to be contained inthe concave portion 334. In the first modification of the secondembodiment, the first resin substrate 230 a provided with through holes230A, the second and third resin substrates 230 b and 230 c which arenot provided with through holes are bonded to one another throughbonding resin layers (bonding plates) 238 a and 238 b, thereby forming acore substrate 230 provided with a concave portion 335 containing chipcapacitors 220 to allow a plurality of chip capacitors 220 to becontained in the concave portion 335.

A process of manufacturing the printed circuit board according to thefirst modification of the second embodiment of the present inventionwill be described hereinafter with reference to FIGS. 21 and 22.

(1) A copper-clad laminated plate 231M having copper foils 232 laminatedon the both sides of resin substrates 231 a each having a core having athickness of 0.3 mm and made of glass cloth or the like which a BT(Bismaleimide-Triazine) resin is impregnated into and hardened in, isemployed as a starting material (FIG. 21(A)). The copper foils 232 ofthe copper-clad laminated plate 231M are etched into a pattern fashion,thereby forming the second and third resin substrates 230 b and 230 ceach having the conductor circuits 235 provided on the both sidesthereof. Also, the copper foils 232 are etched into a pattern fashionand a through hole 230A is formed, thereby forming the first resinsubstrate 230 a having conductor circuits 235 (FIG. 21(B)). The secondresin substrate 230 b is superposed on the third resin substrate 230 cthrough the bonding resin layer (bonding plate) 238 b having a core madeof glass cloth or the like and impregnated with an epoxy resin.Likewise, the first resin substrate 230 a having the through hole 230Aformed therein is superposed on the second resin substrate 230 b throughthe bonding resin layer (bonding plate) 238 a having the through hole238A formed therein (FIG. 21(C)).(2) The superposed substrates are pressurized using a thermal press,thereby integrating the first, second and third resin insulatingsubstrates 230 a, 230 b and 230 c in a multi-layer manner and formingthe core substrate 230 provided with a concave portion 335 forcontaining chip capacitors 220 (FIG. 21(D)). First, by pressuring thesubstrates, the epoxy resin (insulating resin) of the bonding resinlayers 238 a and 238 b is pushed outside and the epoxy resin is madehermetic contact with the first, second and third resin substrates 230a, 230 b and 230 c. Further, since the substrates are pressurized and,at the same time, heated, the first resin substrate 230 a, the secondresin substrate 230 b and the third resin substrate 230 c are fixedlybonded to one another by interposing the bonding resin layers 238 a and238 b as bonding plates.(3) Then, using a printer, thermosetting or UV hardening bondingmaterials 236 are applied onto the base of the concave portion 335 (FIG.21(E)). Alternatively, potting may be conducted instead of theapplication of the bonding materials.(4) Next, a plurality of chip capacitors 220 are mounted on the bondingmaterial 236 (FIG. 22). By containing a plurality of chip capacitors 220in the core substrate, the high integration of capacitors can berealized.(5) Thereafter, a thermosetting resin is filled between the chipcapacitors 220 in the concave portion 335, heated and hardened tothereby form a resin layer 233 (FIG. 22(B)). As the thermosetting resin,an epoxy resin, a phenol resin, a polyimide resin and a triazine resinare preferable. Consequently, the chip capacitors 220 within the concaveportion 335 is fixed and the gaps between the chip capacitors 220 andthe wall surface of the concave portion 335 are filled with the resin.(6) Thermosetting epoxy resin sheets are laminated by vacuum pressingonto the substrate 230 which has been subjected to the above-statedsteps, at a pressure of 5 kg/cm² while raising temperature to 50 to 150°C. to thereby provide interlayer resin insulating layers 240 made of anepoxy resin (FIG. 22(C)).(7) Next, openings 42 for via holes reaching the first terminals 221 andthe second terminals 222 of the chip capacitors 220 are formed in theinterlayer resin insulating layer 240 at the resin substrate 230 a sideby applying laser (FIG. 22(D)).

Later steps are the same as those of (8) to (21) in the first embodimentstated above, which description will not be, therefore, given herein.

First Other Example of First Modification of Second Embodiment

Next, a printed circuit board according to the first other example ofthe first modification of the second embodiment of the present inventionwill be described with reference to FIG. 24. The printed circuit boardin the first other example is almost the same as that in the firstmodification of the second embodiment stated above. However, only thechip capacitors 220 contained in the core substrate 230 are provided inthe first modification of the second embodiment, whereas mass storagechip capacitors 286 are mounted on the front and reverse sides of a coresubstrate in the first other example.

An IC chip momentarily consumes high power and performs complexarithmetic operation. Here in this first modification, to supply highpower to the IC chip, chip capacitors 220 and chip capacitors 286 forpower supply are provided. The advantage derived from these chipcapacitors will be described with reference to FIG. 12.

FIG. 12 is a graph with a vertical axis indicating voltage supplied tothe IC chip and a horizontal axis indicating time. In FIG. 12, two-dotchain line C denotes the voltage variation of a printed circuit boardwhich is not provided with power supply capacitors. If power supplycapacitors are not provided, voltage attenuates greatly. A broken line Adenotes the voltage variation of a printed circuit board having chipcapacitors mounted on the surfaces thereof. Compared with the two-dotchain line C, voltage does not drop greatly. However, since loop lengthis larger, rate-controlled power supply cannot be conductedsufficiently. Namely, at the start of the supply of power, voltagefalls. Further, a two-dot chain line B denotes the voltage drop of aprinted circuit board including the chip capacitors described above withreference to FIG. 23. In this case, loop length can be shortened;however, mass storage chip capacitors cannot be contained in a coresubstrate 230 and voltage, therefore, varies. Here, a solid line Edenotes the voltage variation of the printed circuit board in themodification which printed circuit board has the chip capacitors 220mounted in the core substrate and the mass storage chip capacitors 286mounted on the surfaces thereof. Voltage variation is minimized byproviding the chip capacitors 220 and the mass storage chip capacitors286 (having relatively high inductance) in the vicinity of the IC chip.

Furthermore, as shown in FIG. 13(A), in the chip capacitor 220 of theprinted circuit board in the first other example of the secondembodiment, after the coating layer (not shown) of the first and secondelectrodes 221 and 222 are completely separated, the first and secondelectrodes 221 and 222 are coated with copper plated films 29. The firstand second electrodes 221 and 222 each coated with the copper platedfilm 29 are electrically connected to each other by a via hole 260 madeof a copper plated material. Here, the electrodes 221 and 222 of thechip capacitor are made by metalization and have irregular portions onthe surfaces thereof. Due to this, if the substrate is used whileexposing the metal layers, resin may sometimes remain on the irregularportions in the step of providing non-penetrating holes 242 in theconnection layer 240. At this time, the resin residue causes connectiondefects between the first, second electrodes 221 and 222 and the viaholes 260. In the first other example, by contrast, since the surfacesof the first and second electrodes 221 and 222 are smoothed by thecopper plated films 29, no resin remains when providing non-penetratingholes 42 in the coated interlayer resin insulating layer 240 on theelectrodes and the reliability of the connection between the electrodes221, 222 and the via holes 260 when forming the via holes 260 can beenhanced.

Furthermore, the via holes 260 are formed by plating in the electrodes221 and 222 having the copper plated films 29 formed thereon,respectively, the connection characteristics between the electrodes 221,222 and the via holes 260 is good and disconnection does not occurbetween the electrodes 221, 222 and the via holes 260 even if a heatcycle test is conducted. Besides, no migration occurs and nodisadvantages are derived in the connection portions of the via holes ofthe capacitors.

The copper plated films 29 are provided after the nickel/tin layer(coating layer) coated on the surface of each metal layer 26 in a phaseof manufacturing chip capacitors is separated in a phase of mounting thechip capacitors on the printed circuit board. Alternatively, the copperplated films 29 can be directly coated on the metal layers 26 in thephase of manufacturing the chip capacitors 220. Namely, in the firstother example, as in the case of the second embodiment, after openingsreaching the copper plated films 29 of the electrodes are provided byapplying laser, a de-smear process is performed to thereby form viaholes by copper plating. Accordingly, even if an oxide film is formed onthe surface of the copper plated film 29, the oxide film can be removedby the laser and de-smear processes, thereby making it possible toestablish connection appropriately.

Further, rough layers 23 a are provided on the surfaces of a dielectric23 of the chip capacitors 220 which dielectric is made of ceramic. Dueto this, the adhesiveness between the chip capacitors 220 made ofceramic and the interlayer resin insulating layer 240 made of a resin ishigh and the interlayer resin insulating layer 240 is not separated onthe interface therebetween even if a heat cycle test is conducted. Therough layers 23 a can be formed by polishing the surfaces of the chipcapacitors 220 after sintering them or by roughing the surfaces beforesintering them. In the first other example, the surfaces of thecapacitors are roughed and the adhesiveness between the capacitors andthe resin is thereby enhanced. Alternatively, a silane coupling processcan be conducted to the surfaces of the capacitors.

As shown in FIG. 13(B), it is also possible to employ the first andsecond electrodes 21 and 22 of the first and second capacitors 220 whileremoving part of the coats 28 of the electrodes 21 and 22. This isbecause connection characteristics can be enhanced by exposing the firstand second electrodes 221 and 222.

Second Modification of Second Embodiment

Next, the constitution of a printed circuit board according to thesecond modification of the second embodiment will be described withreference to FIG. 14.

The printed circuit board in the second modification is almost the samein constitution as the printed circuit board in the first embodimentstated above. They, however, differ in chip capacitors 20 contained inthe core substrate 30. FIG. 14 is a plan view of chip capacitors. FIG.14(A) shows a chip capacitor before being cut for providing a pluralityof chip capacitors. In FIG. 14(A), a dashed line denotes a cut line. Asshown in FIG. 14(B), in the printed circuit board in the firstembodiment stated above, the first electrodes 21 and the secondelectrodes 22 are provided on the edges of the chip capacitor. FIG.14(C) shows a chip capacitor before being cut for providing a pluralityof chip capacitors in the second modification. In FIG. 14(C), a dashedline denotes a cut line. In the printed circuit board in the secondmodification, as shown in the plan view of FIG. 14(D), first electrodes21 and second electrodes 22 are provided inside of the edges of the chipcapacitor.

In the printed circuit board in the second modification, the chipcapacitors 20 each having electrodes formed inside of the outer edgesthereof are employed, so that mass storage chip capacitors can beemployed.

Next, a printed circuit board according to the first other example ofthe second modification will be described with reference to FIG. 15.

FIG. 15 is a plan view of a chip capacitor 20 contained in the coresubstrate of the printed circuit board according to the first otherexample. In the first embodiment stated above, a plurality of smallstorage chip capacitors are contained in the core substrate. In thefirst other example, by contrast, a large, mass storage chip capacitor20 is contained in the core substrate. The chip capacitor 20 consists ofthe first electrodes 21, the second electrodes 22, a dielectric 23,first conductive films 24 connected to the first electrodes 21, secondconductive films 25 connected to the second electrodes 22, andelectrodes 27 which are not connected to the first and second conductivefilms 24 and 25, for the connection of the upper and lower surfaces ofthe chip capacitor. The IC chip and the daughter board are connected toeach other through the electrodes 27.

Since the large chip capacitor 20 is employed in the printed circuitboard in the first modification, it is possible to employ a mass storagechip capacitor. Further, since the large chip capacitor 20 is employed,the printed circuit board does not warp even if a heat cycle isperformed repeatedly.

Next, a printed circuit board according to the second other example ofthe second modification will be described with reference to FIG. 16.FIG. 16(A) shows a chip capacitor before being cut for providing aplurality of chip capacitors. In FIG. 16(A), a dashed line denotes anordinary cut line. FIG. 16(B) is a plan view of the chip capacitors. Asshown in FIG. 16(B), a plurality of (or in FIG. 16(B), three) chipcapacitors for providing multiple capacitors are coupled to one anotherand employed as a large capacitor as a whole.

In the second other example, since the large chip capacitor 20 isemployed, it is possible to employ a mass storage chip capacitor.Further, since the large chip capacitor is employed, the printed circuitboard does not warp even if a heat cycle is performed repeatedly.

In the embodiment stated above, the chip capacitors are built in theprinted circuit board. Alternatively, plate-like capacitors eachconstituted by providing a conductive film on a ceramic plate may beemployed instead of the chip capacitors.

As stated above, according to the second embodiment, it is possible tocontain the capacitors in the core substrate and to shorten the distancebetween the IC chip and the capacitors, thereby reducing the loopinductance of the printed circuit board. Further, since the coresubstrate is formed by providing a plurality of resin substrates havingconductor circuits formed thereon in a multilayer manner, the wiringdensity within the core substrate is increased and the number ofinterlayer resin insulating layers can be reduced.

Moreover, since the resin is filled between the core substrate and thecapacitors, a stress resulting from the capacitors or the like can bereduced even if it occurs and no migration occurs. Due to this, there isno fear that the electrodes of the capacitors are separated from theconnection sections of the via holes and dissolved. Thus, it is possibleto maintain desired performance even if a reliability test is executed.

In addition, even if the capacitors are coated with copper, it ispossible to prevent the occurrence of migration.

Third Embodiment

The constitution of a printed circuit board according to the thirdembodiment of the present invention will be described hereinafter withreference to FIGS. 30 and 31. FIG. 30 is a cross-sectional view of aprinted circuit board 410. FIG. 31 shows a state in which an IC chip 490is mounted on the printed circuit board 410 shown in FIG. 30 and thatthe printed circuit board 410 is attached to a daughter board 495.

As shown in FIG. 30, the printed circuit board 410 consists of a coresubstrate 430 containing a plurality of chip capacitors 420, and buildupwiring layers 480A and 480B. Each of the buildup wiring layers 480A and480B consists of interlayer resin insulating layers 540 and 541.Conductor circuits 558 and via holes 560 are formed on the interlayerresin insulating layer 540 of each of the buildup wiring layers 480A and480B. Conductor circuits 559 and via holes 564 are formed on theinterlayer rein insulating layer 541 of each of the buildup wiringlayers 480A and 480B. Solder resist layers 470 are formed on theinterlayer resin insulating layers 541, respectively. Via holes 460 andconductor circuits 458 to be connected to the chip capacitors 420 areprovided on the core substrate 430. The buildup wiring layers 480A and480B are connected to each other by way of through holes 456 formed inthe core substrate 430.

As shown in FIG. 30, each of the chip capacitors 420 consists of thefirst electrode 421, the second electrode 422 and a dielectric 423 putbetween the first and second electrodes. A plurality of pairs of firstconductive films 424 connected to the first electrode 421 side andsecond conductive films 425 connected to the second electrode 422 sideare arranged on the dielectric 423 to face one another.

As shown in FIG. 31, solder bumps 476U to be connected to the pads 492E,492P and 4925 of the IC chip 490 are provided on the upper buildupwiring layer 480A. Solder bumps 476D to be connected to the pads 494E1,494E2, 494P1, 494P2 and 494S of the daughter board 495 are provided onthe lower buildup wiring layer 480B.

The signal pad 4925 of the IC chip 490 is connected to the signal pad494S of the daughter board 495 through the bump 476U—the conductorcircuit 559—the via hole 564—the conductor circuit 558—the via hole560—the through hole 456—the via hole 560—the conductor circuit 558—thevia hole 564—the conductor circuit 559—the bump 476D.

The grounding pad 492E of the IC chip 490 is connected to the firstelectrodes 421 of the chip capacitors 420 through the bumps 476U—the viaholes 564—the conductor circuits 558—the via holes 560—the conductorcircuits 458—the via holes 460. The grounding pad 494E1 of the daughterboard 495 is connected to the first electrodes 421 of the chipcapacitors 420 through the bumps 476D—the via holes 564—the conductorcircuits 558—the via holes 560—the through holes 456—the conductorcircuits 458—the via holes 460. The grounding pad 494E2 is connected tothe first electrodes 421 of the chip capacitors 420 through the bumps476D—the via holes 564—the conductor circuits 558—the via holes 560—theconductor circuits 458—the via holes 460.

The power supply pad 492P of the IC chip 490 is connected to the secondelectrodes 422 of the chip capacitors 420 through the bumps 476U—the viaholes 564—the conductor circuits 558—the via holes 560—the conductorcircuits 458—the via holes 460. The power supply pad 494P1 of thedaughter board 495 is connected to the second electrodes 422 of the chipcapacitors 420 through the bumps 476D—the via holes 564—the conductorcircuits 558—the via holes 560—the through holes 456—the conductorcircuits 458—the via holes 460. The power supply pad 494P2 is connectedto the first electrodes 422 of the chip capacitors 420 through the bumps476D—the via holes 564—the conductor circuits 558—the via holes 560—theconductor circuits 458—the via holes 460. In this embodiment, thedaughter board 495 side is connected to the first and second electrodes421 and 422 of the chip capacitors 420 through the through holes 456. Itis also possible to connect the daughter board 495 side thereto withoutemploying the through holes.

As shown in FIG. 30, the core substrate 430 in this embodiment consistsof the first resin substrate 430 a to which the chip capacitors 420 areconnected through bonding materials, the second resin substrate 430 bconnected to the first resin substrate 430 a through a bonding resinlayer (bonding plate) 438 a and the third resin substrate 430 cconnected to the second resin substrate 430 b through a bonding resinlayer (bonding plate) 438 b. An opening 430B capable of containing thechip capacitors 420 are formed in the second resin substrate 430 b.

With this structure, the chip capacitors 420 can be contained in thecore substrate 430, so that the distance between the IC chip 490 andeach chip capacitor 420 is shortened and the loop inductance of theprinted circuit board 410 can be reduced. Further, the core substrate430 is constituted by providing the first resin substrate 430 a, thesecond resin substrate 430 b and the third resin substrate 430 c in amultilayer manner, the core substrate 430 can obtain sufficientstrength. Moreover, since the core substrate 430 is constituted smoothlyby providing the first resin substrate 430 a and the third resinsubstrate 430 c on the both sides of the core substrate 430,respectively, it is possible to appropriately form the interlayer resininsulating layers 540, 541, the conductor circuits 558, 559 and the viaholes 560 and 564 on the core substrate 430 and the probability of theoccurrence of defective printed circuit boards can be decreased.

Furthermore, in this embodiment, the via holes 460 are provided on theboth sides of the core substrate 430. This makes it possible to connectthe daughter board 495 to each chip capacitors 420 at the shortestdistance and high electric power can be supplied momentarily from thedaughter board to the IC chip.

Moreover, in this embodiment, as shown in FIG. 25(D), an insulatingbonding agent 436 is interposed between the first resin substrate 430 aand each of the chip capacitors 420. Here, the coefficient of thethermal expansion of the bonding agent 436 is set lower than that of thecore substrate 430, i.e., set close to that of the chip capacitors 420made of ceramic. Due to this, even if an internal stress resulting fromthe difference in the coefficient of thermal expansion among the coresubstrate, the bonding layers 436 and the chip capacitors 420, occurs ina heat cycle test, cracks, separation and the like less occur to thecore substrate, making it possible to attain high reliability. It isalso possible to prevent the occurrence of migration.

A method of manufacturing the printed circuit board described above withreference to FIG. 30 will be described with reference to FIGS. 25 to 30.

(1) A one-sided copper-clad laminated plate 430M (first resin substrate430 a or the third resin substrate 430 c) having a copper foil 432laminated on one side of the resin substrate having a core having athickness of 0.1 mm and made of glass cloth or the like which a BT(Bismaleimide-Triazine) resin is impregnated into and hardened in, isemployed as a starting material (FIG. 25(A)).

Next, the copper foil 432 of the copper-clad laminated plate 430M isetched into a pattern, thereby forming openings 432 a for forming viaholes are formed (FIG. 25(B)).

(2) Using a printer, a thermosetting or UV hardening bonding material436 is applied onto portions of the first resin substrate 430 a on whichthe copper foil 432 is not laminated (FIG. 25(C)). Instead of theapplication of the bonding material, potting may be performed.

Next, a plurality of chip capacitors 420 made of ceramic are mounted onthe bonding material 436 and bonded to the first resin substrate 430 athrough the bonding material 436 (FIG. 25(D)). Either one or a pluralityof chip capacitors 420 may be provided; however, if a plurality of chipcapacitors 420 are employed, the high integration of the capacitors canbe realized.

(3) Then, resin layers for bonding (bonding resin layers) 438 a and 438b each having a core made of glass cloth or the like and impregnatedwith an epoxy resin as well as the second resin layer 430 b (having athickness of 0.4 mm) having a core made of glass cloth or the like whicha BT resin is impregnated into and hardened in, are prepared. Openings36A and 430B capable of containing the chip capacitors 420 are formed inthe bonding resin layer 438 a and the second resin layer 430 b,respectively. First, the second resin substrate 430 b is mounted on thethird resin substrate 430 c through the bonding resin layer 438 b withthe surface of the third resin substrate 430 c laminated with the copperfoil 432 directed downward. Next, the first resin substrate 430 a isinverted and mounted on the second resin substrate 430 b through thebonding resin layer 438 a. Namely, the first resin substrate 430 a issuperposed on the second resin substrate 430 b so that the chipcapacitors 420 connected to the first resin substrate 430 a are directedtoward the bonding rein layer 438 a side and can be contained in theopening 430B formed in the second resin substrate 430 b (FIG. 26(A)). Bydoing so, the chip capacitors 420 can be contained in the core substrate430 and the printed circuit board having reduced loop inductance can beprovided.

It is noted that a substrate made of ceramic or AIN cannot be used asthe core substrate. This is because such a substrate has poorworkability for the outside shape thereof, sometimes cannot containcapacitors and has gaps even if filled with a resin.

(4) The superposed substrates are pressurized using a thermal press,thereby integrating the first, second and third resin substrates 430 a,430 b and 430 c in a multilayer manner and forming the core substrate430 having a plurality of chip capacitors 420 (FIG. 26(B)).

First, by pressurizing the substrates, the epoxy resin (insulatingresin) is pushed outside of the bonding resin layers 438 a and 438 b andthe gaps between the opening 430B and the chip capacitors 420 are filledwith the resin. Further, since the substrates are pressurized and, atthe same time, heated, the epoxy resin is hardened and the first resinsubstrate 430 a, the second resin substrate 430 b and the third resinsubstrate 430 c are strongly bonded to one another by interposing thebonding rein layers 438 a and 438 b as bonding resin (bonding plates).In this embodiment, the space within the opening 430B is filled with theepoxy resin flowing out of the bonding resin layers. Alternatively,filler can be provided in the opening 430B.

Since the both sides of the core substrate 430 are the first resinsubstrate 430 a and the third resin substrate 430 c which are smooth,respectively, the interlayer resin insulating layers 540, 541, theconductor circuits 558, 559 and the via holes 560 and 564 can beappropriately formed in steps to be described later without damaging thesmoothness of the core substrate 430 and the probability of theoccurrence of defective printed circuit boards can be decreased.Further, the core substrate 430 can obtain sufficient strength.

(5) Next, the exposed regions of the copper foil 432 from the openings432 a for forming the via holes are removed by applying laser andopenings 442 for via holes reaching the first and second electrodes 421and 422 of the chip capacitors 420 are formed. Namely, using the copperfoil 432 as a conformal mask, the openings 442 for via holes are formedin the core substrate 430 by applying laser. Then, the same step isexecuted to the other side of the substrate (FIG. 26(C)).

As a result, the opening diameters of the via holes depend on theopening diameters of the openings 432 a of the copper foil 432 forforming the via holes, thereby making it possible to form each via holeto have an appropriate diameter. Likewise, the positional accuracy ofthe via hole openings depend on the opening positions of the openings432 a of the copper foil 432 for forming the via holes, thereby makingit possible to form the via holes at appropriate positions even if thepositional accuracy of the laser application is low.

(6) Penetrating holes 444 for through holes are formed in the coresubstrate 430 by drilling or applying laser (FIG. 26(D)). Thereafter, ade-smear process is performed using oxygen plasma. Alternatively, ade-smear process using chemicals such as permanganate may be performed.(7) Next, using SV-4540 manufactured by ULVAC JAPAN, Ltd., a plasmaprocess is performed to form rough surfaces on the entire surfaces ofthe core substrate 430. The plasma process is performed for two minuteswhile using, as inert gas, argon gas on conditions of power of 200 W, agas pressure of 0.6 Pa and a temperature of 70° C. Then, sputtering isperformed with Ni and Cu as targets and Ni—Cu metal layers 448 areformed on the surfaces of the core substrate 430, respectively (FIG.27(A)). While sputtering is employed herein, metal layers of copper,nickel or the like may be formed by electroless plating. In some cases,after performing sputtering, electroless plated films may be formed. Aroughing process may be performed using an acid or an oxidizer. Therough layers are preferably 0.1 to 5 μm thick.(8) Next, photosensitive dry films are bonded onto the surfaces of theNi—Cu metal layers 448 and exposure and development processes areperformed while mounting masks, thereby forming resists 450 each havinga predetermined pattern. The core substrate 430 is then immersed in anelectroplating solution, current is applied to the substrate 430 throughthe Ni—Cu metal layers 448 and electroplating is conducted to portionsin which the resists 450 are not formed on the following conditions,thereby forming electroplated films 452 (FIG. 27(B)).

[Electroplating Solution]

Sulfuric acid 2.24 mol/l Copper sulfate 0.26 mol/l Additive (KaparacidHL 19.5 mol/l manufactured by Atotech Japan

[Electroplating Conditions]

Current density 1 A/dm² Duration 120 minutes Temperature 22 ± 2° C.(9) After separating and removing the resists 450 with 5% NaOH, theNi—Cu metal layers 448 and the copper foil 432 under the resists 450 aredissolved and removed by etching with an etching solution of a mixtureof a nitride acid, a sulfuric acid and hydrogen peroxide, therebyforming conductor circuits 458 (including via holes 460) and throughholes 456 each consisting of the copper foil 432, the Ni—Cu metal layer448 and the electroplated copper film 452. After washing and drying theresultant substrate, an etching solution is sprayed on the both sides ofthe substrate and the surfaces of the conductor circuits 458 (includingthe via holes 460) and the through holes 456 are etched, thereby formingrough layers 462 on the entire surfaces of conductor circuits 458(including the via holes 460) and the through holes 456 (FIG. 27(C)). Asthe etching solution, a mixture of 10 parts by weight of an imidazolecopper (II) complex, 7 parts by weight of an glycolic acid, 5 parts byweight of potassium chloride and 78 parts by weight of ion-exchangewater is employed.(10) Resin filler 464 mainly consisting of an epoxy resin is applied onthe both sides of the substrate 430 using the printer, thereby fillingthe resin filler 464 between the conductor circuits 458 and in thethrough holes 456, and heating and drying the resin filler 464. Namely,by executing this step, the resin filler 464 is filled between theconductor circuits 458 and in the via holes 460 and the through holes456 (FIG. 25(D)).(11) One side of the substrate 430 for which the process described in(10) above has been completed, is polished by belt sander polishingusing belt abrasive paper (manufactured by Sankyo Rikagaku Co., Ltd.) insuch a manner that the resin filler 464 is not left on the surfaces ofthe conductor circuits 458 and the land surfaces 456 a of the throughholes 456. Then, buffing is performed to remove flaws caused by the beltsander polishing. These series of polishing are also conducted to theother side of the substrate 430. Next, the resin filler 464 thus filledis heated an hardened. Thus, it is possible to obtain a wiring substratewherein the surface layer portion of the resin filler 464 filled in thethrough holes 456 and the like and rough surfaces 462 on the uppersurfaces of the conductor circuits 458 are removed, the both sides ofthe substrate 430 are smoothed, the resin filer 464 and the conductorcircuits 458 are strongly bonded to one another through the roughsurfaces 462, and the inner walls of the through holes 456 and the resinfiller 464 are strongly bonded to one another through the rough surfaces462.

Next, the same etching solution as that employed in (9) above is sprayedon the both sides of the substrate 430 to etch the surfaces of theconductor circuits 458 and the land surfaces 456 a of the through holes456 which have been flattened once, thereby forming rough surfaces 458 aon the entire surfaces of the conductor circuits 458 (FIG. 28(A)).

(12) Thermosetting epoxy resin sheets to be described later arelaminated by vacuum pressing onto the substrate 430 which has beensubjected to the above-stated steps, at a pressure of 5 kg/cm² whileraising temperature to 50 to 150° C., to thereby provide interlayerresin insulating layers 540 (FIG. 28(B)). The degree of vacuum duringvacuum pressing is 10 mmHg.(13) Next, openings 542 for via holes are formed in the interlayer resininsulating layers 540 by applying laser (FIG. 28(C)).(14) Using SV-4540 manufactured by ULVAC JAPAN, Ltd. employed in thestep of (7), a plasma process is performed to form rough surfaces 540 aon the surfaces of the interlayer resin insulating layers 540 (FIG.28(D)). Here, as in the case of the step of (7), a rouging process maybe performed by using either an acid or an oxidizer. The rough layersare preferably 0.1 to 5 μm thick.(15) Thereafter, as in the case of the step of (7), sputtering isperformed with Ni and Cu as targets, to thereby form Ni—Cu metal layers548 on the surfaces of the interlayer resin insulating layers 540 (FIG.29(A)). While sputtering is performed herein, metal layers of copper,nickel or the like may be formed by electroless plating. In some cases,after forming the metal layers by sputtering, electroless plated filmsmay be formed.(16) Then, as in the case of the step of (8), photosensitive dry filmsare bonded onto the surfaces of the Ni—Cu metal layers 548 and exposureand development processes are performed while mounting masks, therebyforming resists 544 each having a predetermined pattern. The coresubstrate is then immersed in an electroplating solution, current isapplied to the substrate through the Ni—Cu metal layers 548 andelectroplating is conducted to portions in which the resists 544 are notformed, thereby forming electroplated films 552 (FIG. 29(B)).(17) Thereafter, the same process as in the step of (9) is performed tothereby form conductor circuits 558 (including via holes 560) eachconsisting of the Ni—Cu metal layer 548 and the electroplated film 552.After washing and drying the resultant substrate, an etching solution issprayed on the both sides of the substrate, which are thus etched,thereby forming rough surfaces 154 on the entire surfaces of theconductor circuits 558 (including the via holes 560) (FIG. 29(C)).(18) The steps of (12) to (17) are further repeated, thereby forminginterlayer resin insulating layers 541, conductor circuits 559(including via holes 564) and rough surfaces 565 further above (FIG.29(D)).

Later steps are the same as those of (16) to (19) in the firstembodiment stated above, which description will not be, therefore, givenherein.

The mounting of the IC chip 490 on the printed circuit board 410completed through the above steps and the attachment of the printedcircuit board 410 to the daughter board 495 are the same as those in thefirst embodiment, which description will not be, therefore, givenherein.

First Other Example of Third Embodiment

A printed circuit board according to the first other example of thethird embodiment of the present invention will be described hereinafterwith reference to FIG. 32. The printed circuit board in the first otherexample is almost the same as the printed circuit board in the thirdembodiment stated above. However, in the printed circuit board in thefirst other example, conductive connection pins 496 are provided at theprinted circuit board and the printed circuit is connected to a daughterboard through the conductive connection pins 496.

Further, in the third embodiment stated above, only the chip capacitors420 contained in the core substrate 430 are provided. In this example,mass storage chip capacitors 486 are mounted on the front and reversesides of the substrate.

The IC chip momentarily consumes high power and performs complexarithmetic operation. In the first other example, to supply high powerto the IC chip, chip capacitors 420 and chip capacitors 486 for powersupply are provided. The advantage derived from these chip capacitorswill be described with reference to FIG. 12.

FIG. 12 is a graph with a vertical axis indicating voltage supplied tothe IC chip and a horizontal axis indicating time. In FIG. 12, two-dotchain line C denotes the voltage variation of a printed circuit boardwhich is not provided with power supply capacitors. If power supplycapacitors are not provided, voltage attenuates greatly. A broken line Adenotes the voltage variation of a printed circuit board having chipcapacitors mounted on the surfaces thereof. Compared with the two-dotchain line C, voltage does not drop greatly. However, since loop lengthis larger, rate-controlled power supply cannot be conductedsufficiently. Namely, at the start of the supply of power, voltagefalls. Further, a two-dot chain line B denotes the voltage drop of aprinted circuit board including the chip capacitors described above withreference to FIG. 31. In this case, loop length can be shortened;however, mass storage chip capacitors cannot be contained in a coresubstrate 430 and voltage, therefore, varies. Here, a solid line Edenotes the voltage variation of the printed circuit board in the firstother example which printed circuit board has the chip capacitors 420mounted in the core substrate and the mass storage chip capacitors 486mounted on the surfaces thereof. Voltage variation is minimized byproviding the chip capacitors 420 and the mass storage chip capacitors486 (having relatively high inductance) in the vicinity of the IC chip.

First Modification of Third Embodiment

Next, a printed circuit board 414 according to the first modification ofthe third embodiment will be described with reference to FIG. 36. Theprinted circuit board in the first modification of the third embodimentis almost the same in constitution as the printed circuit board in thethird embodiment stated above. In the third embodiment described abovewith reference to FIG. 30, each conductor circuit 458 consists of threelayers, i.e., the copper foil 432, the Ni—Cu metal layer 448 and theelectroplated film 452. In the printed circuit board 414 in the firstmodification of the third embodiment, by contrast, each conductorcircuit 458 consists of two layers, i.e., an electroless plated film 443and an electroplated film 452. Namely, the copper foil 432 is removedand thickness is reduced, thereby forming the conductor circuit 458 atfine pitch.

In addition, in the printed circuit board 414 in the first modificationof the third embodiment, conductor circuits 435 are formed on the bothsides of the second resin substrate 430 b provided with an opening 430Bfor containing chip capacitors 420. In the first modification of thethird embodiment, since the conductor circuits 435 are formed on theboth sides of the second resin substrate 430 b provided with the opening430B for containing the chip capacitors 420, it is possible to increasewiring density within the core substrate 430 and to reduce the number ofinterlayer resin insulating layers to be built up.

Furthermore, as shown in FIG. 13(A), in the chip capacitor 420 of theprinted circuit board in the first modification of the third embodiment,after the coating layer (not shown) of the first and second electrodes421 and 422 are completely separated, the first and second electrodes421 and 422 are coated with copper plated films 29. The first and secondelectrodes 421 and 422 each coated with the copper plated film 29 areelectrically connected to each other by via holes 460 made of a copperplated material. Here, the electrodes 421 and 422 of the chip capacitorare made by metalization and have irregular portions on the surfacesthereof. Due to this, if the substrate is used while exposing the metallayers, the resin may sometimes remain on the irregular portions in thestep of providing non-penetrating holes 442 in the first resin substrate430 a. At this time, the resin residue causes connection defects betweenthe first, second electrodes 421, 422 and the via holes 460. In thefirst modification of the third embodiment, by contrast, since thesurfaces of the first and second electrodes 421 and 422 are smoothed bythe copper plated films 29, no resin remains when providing openings 442in the coated first resin substrate 430 a on the electrodes and thereliability of the connection between the electrodes 421, 422 and thevia holes 460 when forming the via holes 460 can be enhanced.

Furthermore, the via holes 460 are formed by plating in the electrodes421 and 422 having the copper plated films 29 formed thereon,respectively, the connection characteristic between the electrodes 421,422 and the via holes 460 is good and disconnection does not occurbetween the electrodes 421, 422 and the via holes 460 even if a heatcycle test is conducted. Besides, no migration occurs and nodisadvantages are derived in the connection section of the via holes ofthe capacitors.

The copper plated films 29 are provided after the nickel/tin layer(coating layer) coated on the surface of each metal layer 26 in a phaseof manufacturing chip capacitors is separated in a phase of mounting thechip capacitors on the printed circuit board. Alternatively, the copperplated films 29 can be directly coated on the metal layers 26 in thephase of manufacturing the chip capacitors 420. Namely, in the firstmodification of the third embodiment, as in the case of the thirdembodiment, after openings reaching the copper plated films 29 of theelectrodes are provided by applying laser, a de-smear process isperformed to thereby form via holes by copper plating. Accordingly, evenif an oxide film is formed on the surface of the copper plated film 29,the oxide film can be removed by the laser and de-smear processes,thereby making it possible to establish connection appropriately.

Further, rough layers 23 a are provided on the surfaces of a dielectric423 of each chip capacitor 420 which dielectric is made of ceramic. Dueto this, the adhesiveness between the chip capacitors 420 made ofceramic and the resin substrates 438 a and 438 b made of a resin is highand the first resin substrate 430 a is not separated on the interfacetherebetween even if a heat cycle test is conducted. The rough layers 23a can be formed by polishing the surfaces of the chip capacitors 420after sintering them or by roughing the surfaces before sintering them.In the first modification of the third embodiment, the surfaces of thecapacitors are roughed and the adhesiveness between the capacitors andthe resin is thereby enhanced. Alternatively, a silane coupling processcan be conducted to the surfaces of the capacitors.

As shown in FIG. 13(B), it is also possible to employ the first andsecond electrodes 21 and 22 of the capacitors 420 while removing part ofthe coats 28 of the electrodes 21 and 22. This is because connectioncharacteristics can be enhanced by exposing the first and secondelectrodes 21 and 22.

A process for manufacturing the printed circuit board according to thefirst modification of the third embodiment of the present invention willbe described with reference to FIGS. 33 to 35.

(1) One-sided copper-clad laminated plates 430M (the first resinsubstrate 430 a and the third resin substrate 430 c) each having acopper foil 432 laminated on one side of a resin substrate having a corehaving a thickness of 0.1 mm and made of glass cloth or the like which aBT (Bismaleimide-Triazine) resin is impregnated into and hardened in, isprepared. Also, a two-sided copper-clad laminated plate 430N (the secondresin substrate 430 b) having a copper foil 432 laminated on the bothsides of a resin substrate having a core having a thickness of 0.4 mmand made of glass cloth or the like which a BT (Bismaleimide-Triazine)resin is impregnated into and hardened in, is prepared (FIG. 33(A)).(2) Next, the copper foil 432 of each copper-clad laminated plate 430Mis etched into a pattern, thereby forming openings 432 a for forming viaholes are formed. Likewise, the copper foils 432 of the both-sidedcopper-clad laminated plate 430N are etched into a pattern, therebyforming conductor circuits 435 (FIG. 33(B)). In the first modificationof the third embodiment, the conductor circuit 435 are formed on theboth sides of the second resin substrate 430 b, so that the wiringdensity of the core substrate can be advantageously increased and thatthe number of interlayer resin insulating layers to be built up can beadvantageously reduce.(3) Using a printer, a thermosetting or UV hardening bonding material436 is applied onto portions of the first resin substrate 430 a on whichthe copper foils 432 are not laminated (FIG. 33(C)). Instead of theapplication of the bonding material, potting may be performed.

Next, a plurality of chip capacitors 420 made of ceramic are mounted onthe bonding material 436 and bonded to the first resin substrate 430 athrough the bonding material 436 (FIG. 33(D)). Either one or a pluralityof chip capacitors 420 may be provided; however, if a plurality of chipcapacitors 420 are employed, the high integration of the capacitors canbe realized.

(4) Then, resin layers for bonding (bonding resin layers) 438 a and 438b each having a core made of glass cloth or the like and impregnatedwith an epoxy resin as well as the second resin layer 430 b areprepared. Openings 36A and 430B capable of containing the chipcapacitors 420 are formed in the bonding resin layer 438 a and thesecond resin layer 430 b, respectively. First, the second resinsubstrate 430 b is mounted on the third resin substrate 430 c throughthe bonding resin layer 438 b with the surface of the third resinsubstrate 430 c laminated with the copper foil 432 directed downward.Next, the first resin substrate 430 a is inverted and mounted on thesecond resin substrate 430 b through the bonding resin layer 438 a.Namely, the first resin substrate 430 a is superposed on the secondresin substrate 430 b so that the chip capacitors 420 can be containedin the opening 430B formed in the second resin substrate 430 b (FIG.34(A)). By doing so, the chip capacitors 420 can be contained in thecore substrate 430 and the printed circuit board having reduced loopinductance can be provided.(5) The superposed substrates are pressurized using a thermal press,thereby integrating the first, second and third resin substrates 430 a,430 b and 430 c in a multilayer manner and forming the core substrate430 having a plurality of chip capacitors 420 (FIG. 34(B)).

In this embodiment, the epoxy resin flowing out of the bonding resinlayers is filled in gaps within the openings 430. Alternatively, fillermay be arranged in the openings 430B.

Since the both sides of the core substrate 430 are the first resinsubstrate 430 a and the third resin substrate 430 c which are smooth,respectively, the interlayer resin insulating layers 540, 541, theconductor circuits 558, 559 and the via holes 560 and 564 can beappropriately formed in steps to be described later without damaging thesmoothness of the core substrate 430 and the probability of theoccurrence of defective printed circuit boards can be decreased.Further, the core substrate 430 can obtain sufficient strength.

(6) Next, the exposed regions of the copper foils 432 from the openings432 a for forming the via holes are removed by applying laser andopenings 442 for via holes reaching the first and second electrodes 421and 422 of the chip capacitors 420 are formed. Namely, using the copperfoils 432 as conformal masks, the openings 442 for the via holes areformed in the core substrate 430. Then, the same step is executed to theother side of the substrate (FIG. 34(C)). As a result, the openingdiameters of the via holes depend on the opening diameters of theopenings 432 a of the copper foils 432 for forming the via holes,thereby making it possible to form each via hole to have an appropriatediameter. Likewise, the positional accuracy of the via hole openingsdepend on the opening positions of the openings 432 a of the copper foil432 for forming the via holes, thereby making it possible to form thevia holes at appropriate positions even if the positional accuracy ofthe laser application is low.(7) Thereafter, the copper foils 432 on the both sides of the coresubstrate 430 are etched by using an etching solution and therebyremoved. By doing so, it is possible to form the thinner conductorcircuits 458 in the later step to be described later and form thecircuits 458 at fine pitch.

Next, penetrating holes 444 for through holes are formed in the coresubstrate 430 by drilling or applying laser (FIG. 34(D)). Thereafter, ade-smear process is performed using oxygen plasma. Alternatively, ade-smear process using chemicals such as permanganate may be performed.

(8) Next, using SV-4540 manufactured by ULVAC JAPAN, Ltd., a plasmaprocess is performed to form rough surfaces 446 on the entire surfacesof the core substrate 430 (FIG. 35(A)). The plasma process is performedfor two minutes while using, as inert gas, argon gas on conditions ofpower of 200 W, a gas pressure of 0.6 Pa and a temperature of 70° C.Alternatively, a roughing process may be performed using an acid or anoxidizer. The rough layers are preferably 0.1 to 5 μm thick.(9) Next, the substrate 430 is immersed in an electroless copper platingsolution having the following composition to thereby form electrolesscopper plated films 443 each having a thickness of 0.6 to 3.0 μm on theentirety of the rough surfaces 446 (FIG. 35(B)).

[Electroless Plating Solution]

NiSO₄ 0.003 mol/l tartaric acid 0.200 mol/l copper sulfate 0.043 mol/lHCHO 0.050 mol/l NaOH 0.100 mol/l α,α′-bipyridyl   40 mg/l polyethyleneglycol (PEG)  0.10 g/l

[Electroless Plating Conditions]

40 minutes at a solution temperature of 35° C.

While electroless plating is employed in this embodiment, metal layersof copper, nickel or the like may be formed by sputtering. In somecases, after forming the layers by sputtering, electroless plated filmsmay be formed.

(10) Commercially available photosensitive dry films are bonded onto theelectroless copper plated films 443. Masks are mounted on the films,respectively and the films are exposed with 100 mJ/cm³ and developedwith a 0.8% sodium carbonate solution, thereby providing plating resists450 each having a thickness of 30 μm. Then, the substrate 430 is washedwith water of a temperature of 50° C. and degreased, washed with waterof a temperature of 25° C. and with a sulfuric acid, and subjected tocopper electroplating on the following conditions, thereby formingelectroplated copper films 452 each having a thickness of 20 μm (FIG.35(C)).

[Electroplating Solution]

Sulfuric acid 2.24 mol/l Copper sulfate 0.26 mol/l Additive 19.5 mol/l(Kaparacid HL manufactured by Atotech Japan)

[Electroplating Conditions]

Current density 1 A/dm² Duration 65 minutes temperature 22 ± 2° C.(11) After separating and removing the resists 450 with 5% NaOH, theelectroless plated films 443 under the resists 450 are dissolved andremoved by etching with an etching solution of a mixture of a sulfuricacid and hydrogen peroxide, thereby forming conductor circuits 458(including via holes 460) and through holes 456 each consisting of theelectroless copper plated film 443 and the electroplated copper film 452each having a thickness of 18 μm (FIG. 35(D)). In the first modificationof the third embodiment, the copper foils 432 are removed in advance asstated above, whereby the conductor films 458 can made thinner andformed at fine pitch. While the copper foils 432 are completelyseparated in this modification, it is also possible to make theconductor circuits 458 thinner and form the conductor circuits 458 atfine pitch by making the copper foils 432 thinner by light etching.

Later steps are the same as those of (10) to (18) in the thirdembodiment stated above, which description will not be, therefore, givenherein.

In the first modification of the third embodiment stated above, the viaholes are provided on the both sides of the core substrate. It is alsopossible to form via holes only on one side of the substrate. Further,the openings 432 a of the copper foils 432 on the surfaces of the coresubstrate 430 are employed as conformal masks in this modification. Itis also possible to provide openings reaching the capacitors by applyinglaser without employing the conformal masks of the core substrate 430.

Second Modification of Third Embodiment

Next, the constitution of a printed circuit board according to thesecond modification of the first embodiment will be described withreference to FIG. 14.

The printed circuit board in the second modification is almost the samein constitution as the printed circuit board in the first embodimentstated above. They, however, differ in chip capacitors 20 contained inthe core substrate 30. FIG. 14 is a plan view of chip capacitors. FIG.14(A) shows a chip capacitor before being cut for providing a pluralityof chip capacitors. In FIG. 14(A), a dashed line denotes a cut line. Asshown in FIG. 14(B), in the printed circuit board in the firstembodiment stated above, the first electrodes 21 and the secondelectrodes 22 are provided on the edges of the chip capacitor. FIG.14(C) shows a chip capacitor before being cut for providing a pluralityof chip capacitors in the second modification. In FIG. 14(C), a dashedline denotes a cut line. In the printed circuit board in the secondmodification, as shown in the plan view of FIG. 14(D), first electrodes21 and second electrodes 22 are provided inside of the edges of the chipcapacitor.

In the printed circuit board in the second modification, the chipcapacitors 20 each having electrodes formed inside of the outer edgesthereof are employed, so that mass storage chip capacitors can beemployed.

Next, a printed circuit board according to the first other example ofthe second modification will be described with reference to FIG. 15.

FIG. 15 is a plan view of a chip capacitor 20 contained in the coresubstrate of the printed circuit board according to the first otherexample. In the first embodiment stated above, a plurality of smallstorage chip capacitors are contained in the core substrate. In thefirst other example, by contrast, a large, mass storage chip capacitor20 is contained in the core substrate. The chip capacitor 20 consists ofthe first electrodes 21, the second electrodes 22, a dielectric 23, thefirst conductive films 24 connected to the first electrodes 21, thesecond conductive films 25 connected to the second electrodes 22,electrodes 27 which are not connected to the first and second conductivefilms 24 and 25, for the connection of the upper and lower surfaces ofthe chip capacitor. The IC chip and the daughter board are connected toeach other through the electrodes 27.

Since the large chip capacitor is employed in the printed circuit boardin the first modification, it is possible to employ a mass storage chipcapacitor. Further, since the large chip capacitor 20 is employed, theprinted circuit board does not warp even if a heat cycle is performedrepeatedly.

Next, a printed circuit board according to the second other example ofthe second modification will be described with reference to FIG. 16.FIG. 16(A) shows a chip capacitor before being cut for providing aplurality of chip capacitors. In FIG. 16(A), a dashed line denotes anordinary cut line. FIG. 16(B) is a plan view of the chip capacitors. Asshown in FIG. 16(B), a plurality of (or in FIG. 16(B), three) chipcapacitors for providing multiple capacitors are coupled to one anotherand employed as a large capacitor as a whole.

In the second other example, since the large chip capacitor 20 isemployed, it is possible to employ a mass storage chip capacitor.Further, since the large chip capacitor 20 is employed, the printedcircuit board does not warp even if a heat cycle is performedrepeatedly.

In the embodiment stated above, the chip capacitors are built in theprinted circuit board. Alternatively, plate-like capacitors eachconstituted by providing a conductive film on a ceramic plate may beemployed instead of the chip capacitors.

The structure of the third embodiment makes it possible to contain thecapacitors in the core substrate and to shorten the distance between theIC chip and each capacitor, thereby reducing the loop inductance of theprinted circuit board. Further, since the printed circuit board isconstituted by providing resin substrates in a multilayer manner, thecore substrate can obtain sufficient strength. Besides, the first resinsubstrate and the third resin substrate are provided on the both sidesof the core substrate, respectively, thereby constituting the coresubstrate smoothly. Thus, it is possible to appropriately forminterlayer resin insulating layers and conductor circuits on the coresubstrate and to thereby decrease the probability of the occurrence ofdefective printed circuit boards.

In addition, by adopting the manufacturing method of the thirdembodiment, the opening diameters of the via holes depend on the openingdiameters of the openings of metal films, so that it is possible to formeach via hole to have an appropriate diameter. Likewise, the positionalaccuracy of the via hole openings depend on the opening positions of theopenings of the metal films, so that it is possible to form the viaholes at appropriate positions even if the positional accuracy of thelaser application is low.

Since it is possible to connect the substrate from the lower portions ofthe capacitors, the structure allows reducing the loop inductance andincreasing the degree of freedom for arrangement.

Moreover, since the resin is filled between the core substrate and thecapacitors, a stress resulting from the capacitors or the like can bereduced even if it occurs and no migration occurs. Due to this, there isno fear that the electrodes of the capacitors are separated from theconnection sections of the via holes and dissolved. Thus, it is possibleto maintain desired performance even if a reliability test is executed.

In addition, even if the capacitors are coated with copper, it ispossible to prevent the occurrence of migration.

Fourth Embodiment

A printed circuit board according to the fourth embodiment of thepresent invention will be described hereinafter with reference to FIGS.42 to 44. FIG. 42 is a cross-sectional view of a printed circuit board610. FIG. 43 shows a state in which an IC chip 690 is mounted on theprinted circuit board 610 shown in FIG. 42 and that the printed circuitboard 610 is attached to a daughter board 694. FIG. 44(A) is an enlargedview of a via hole 660 shown in FIG. 42. FIG. 44(B) is a typical viewshowing a state in which a plurality of via holes 760 are provided inthe via hole 660 shown in FIG. 44(A), which view is seen from an arrow Bside.

As shown in FIG. 42, the printed circuit board 610 consists of a coresubstrate 630 containing a plurality of chip capacitors 620, and buildupwiring layers 680A and 680B. Relatively large via holes 660 areconnected to the electrodes 621 and 622 of the plural chip capacitors620 contained in the core substrate 630. Each of the buildup wiringlayers 680A and 680B consists of interlayer resin insulating layers 740and 741. Conductor circuits 758 and relatively small via holes 760 areformed on the interlayer resin insulating layers 740, whereas conductorcircuits 759 and relatively small via holes 764 are formed on theinterlayer resin insulating layers 741. Solder resist layers 670 areprovided on the interlayer resin insulating layers 741, respectively.

As shown in FIG. 13(A), each of the chip capacitors 620 consists of thefirst electrode 621, the second electrode 622 and a dielectric 23 putbetween the first and second electrodes. A plurality of pairs of thefirst conductive films 24 connected to the first electrode 621 side andthe second conductive films 25 connected to the second electrode 622side are arranged on the dielectric 23 to face one another. It is notedthat as shown in FIG. 13(B), part of coats 28 of the first electrodes 21and the second electrodes 22 of the capacitors 620 can be removed. Thisis because the connection characteristics with respect to the via holesmade by plating can be enhanced by exposing the first and secondelectrodes 21 and 22.

As shown in FIG. 43, solder bumps 676U to be connected to the pads 692of the IC chip 690 are formed on the via hole 764 of the upper buildupwiring layer 680A. Solder bumps 676D to be connected to the pads 694 ofthe daughter board 695 are formed on the via holes 764 of the lowerbuildup wiring layer 680B.

A resin substrate is employed as the core substrate. For example, aresin material used for an ordinary printed circuit board such as aglass epoxy resin impregnated material, a phenol resin impregnatedmaterial or the like can be employed. However, substrates made ofceramic or AIN cannot employed as the core substrate. This is becausesuch a substrate has poor workability for the outside shape thereof,sometimes cannot contain capacitors and has gaps even if filled with aresin.

Also, a plurality of chip capacitors 620 are contained in a concaveportion 734 formed in the core substrate, so that it is possible toarrange the chip capacitors 620 with high density. Further, since aplurality of chip capacitors 620 are contained in the concave portion734, it is possible to make the heights of the chip capacitors 620uniform. Due to this, the thicknesses of the resin layers 640 on thechip capacitors 620 can be made uniform, so that it is possible toappropriately form via holes 660. Besides, since the distance betweenthe IC chip 690 and each chip capacitor 620 becomes shorter, so that itis possible to reduce loop inductance.

In addition, as shown in FIG. 44(A) which is an enlarged view of the viahole 660 shown in FIGS. 42 and 43, a plurality of via holes 760 in theupper buildup wiring layer 680A are connected to one via hole 660. Thelarge via hole 660 as shown in FIG. 44(B) is formed to have an insidediameter of 125 μm and a land diameter of 165 μm, the small via hole 760is formed to have an inside diameter of 25 μm and a land diameter of 65μm. On the other hand, the chip capacitors 620 are formed rectangularlyand the first and the first electrode 621 and the second electrode 621of each capacitor are formed rectangularly to have one side of 250 μm.Due to this, even if the positions at which the chip capacitors arearranged are shifted by several tens of μm, it is possible to establishconnection between the first electrodes 621 and the second electrodes622 of the chip capacitors 620 and the via holes 660, thereby ensuringthe supply of power from the chip capacitors 620 to the IC chip 690.Further, by providing a plurality of via holes 760, the same effect asthat of connecting inductances in parallel. Due to this, the highfrequency characteristics of power supply lines and ground lines areenhanced, thereby making it possible to prevent the malfunction of theIC chip due to lack of supply of power or the variation of earth level.Moreover, since the wiring length to each chip capacitor 620 from the ICchip can be shortened, it is possible to reduce loop inductance.

As shown in FIG. 42, the via holes 660 are formed as filled via holesfilled with a plated material and having flat surfaces. This makes itpossible to directly connect a plurality of via holes 760 onto the viahole 660. Thus, it is possible to enhance the characteristics of theconnection between the via holes 660 and 760 and to ensure the supply ofpower from the chip capacitors 620 to the IC chip 690. In thisembodiment, the filled via holes are formed by filling a plated materialwithin the holes. It is also possible to employ filled via holes eachhaving a metal film provided on the front surface after filling a resinin the holes.

The coefficients of thermal expansion of resin filler 633 and a bondingmaterial 636 below the chip capacitors 620 are set lower than those ofthe core substrate 630 and resin insulating layers 640, i.e., set closeto those of the chip capacitors 620 made of ceramic. Due to this, evenif an internal stress resulting from difference in the coefficient ofthermal expansion occurs among the core substrate 630, the resininsulating layers 640 and the chip capacitors 620 during a heat cycletest, cracks, separation and the like less occurs to the core substrate630 and the resin insulating layers 640, thereby making it possible toattain high reliability.

Furthermore, since through holes 656 are formed in the resin layers 633between the chip capacitors 620, no signal lines pass through the chipcapacitors 620 made of ceramic. Thus, propagation delay caused byreflection due to the discontinuous impedance by a high dielectric andthe passage of the high dielectric does not occur.

As show in FIG. 13(A), in the chip capacitor 620, a copper plated film29 is coated on the surface of a metal layer 26 constituting the firstelectrode 621 and the second electrode 622. The plated film coat isformed by plating such as electroplating and electroless plating. Asshown in FIG. 42, the first and second electrodes 621 and 622 coatedwith the copper plated films 29 are electrically connected to the viaholes 660 made of a copper plated material. Here, the electrodes 621 and622 of the chip capacitors are formed by metalization and have irregularportions on the surfaces thereof. Due to this, if the substrate is usedwhile exposing the metal layers 26, resin may sometimes remain on theirregular portions in a step of providing openings 639 in resininsulating layers 640 as will be described later. At this time, theresin residue causes connection defects between the first, secondelectrodes 621 and 622 and the via holes 660. To prevent this, thesurfaces of the first and second electrodes 621 and 622 are smoothed bythe copper plated films 29. Thus, no resin remains when providing theopenings 639 in the resin insulating layers 640 coated on the electrodesand the reliability of the connection between the electrodes 621, 622and the via holes 660 when forming the via holes 660 can be enhanced.

Furthermore, since the via holes 660 are formed by plating in theelectrodes 621 and 622 having the copper plated films 29 formed thereon,respectively, the characteristic of the connection between theelectrodes 621, 622 and the via holes 660 is high and disconnection doesnot occur between the electrodes 621, 622 and the via holes 660 even ifa heat cycle test is conducted.

The copper plated films 29 are provided after the nickel/tin layer(coating layer) coated on the surface of each metal layer 26 in a phaseof manufacturing chip capacitors is separated in a phase of mounting thechip capacitors on the printed circuit board. Alternatively, the copperplated films 29 can be directly coated on the metal layers 26 in thephase of manufacturing the chip capacitors 220. Namely, in thisembodiment, after openings reaching the copper plated films 29 of theelectrodes are provided by applying laser, a de-smear process isperformed to thereby form via holes by copper plating. Accordingly, evenif an oxide film is formed on the surface of the copper plated film 29,the oxide film can be removed by the laser and de-smear processes,thereby making it possible to establish connection appropriately.

Further, rough layers 23 a may be provided on the surfaces of thedielectrics 23 of the chip capacitors 620 which dielectrics are made ofceramic. By doing so, the adhesiveness between the chip capacitors 620made of ceramic and the interlayer resin insulating layer 640 made of aresin is high and the interlayer resin insulating layer 640 is notseparated on the interface therebetween even if a heat cycle test isconducted. The rough layers 23 a can be formed by polishing the surfacesof the chip capacitors 620 after sintering them or by roughing thesurfaces before sintering them. In this embodiment, the surfaces of thecapacitors are roughed and the adhesiveness between each capacitor andthe resin is thereby enhanced. Alternatively, a silane coupling processcan be conducted to the surfaces of the capacitors.

Next, a method of manufacturing the printed circuit board describedabove with reference to FIG. 42 will be described with reference toFIGS. 37 to 42.

(1) First, a core substrate 630 consisting of an insulating resinsubstrate is employed as starting material (FIG. 37(A)). Next, a concaveportion 734 for providing capacitors therein is formed on one side ofthe core substrate 630 by conducting spot facing or by providing athrough hole in the insulating resin, followed by pressing and bonding(FIG. 37(B)). The concave portion 734 is formed to be wider than an areain which a plurality of capacitors can be arranged. By doing so, it ispossible to ensure that a plurality of capacitors are provided in thecore substrate 630.(2) Then, using a printer, a bonding material 636 is applied onto theconcave portion 734 (FIG. 37(C)). Alternatively, the bonding materialcan be applied onto the concave portion by a potting, a die-bondingmethod, a method of applying a bonding sheet or the like. As the bondingmaterial 636, one having a lower coefficient of expansion than that ofthe core substrate is employed. Next, a plurality of chip capacitors 620made of ceramic are bonded to the concave portion 734 through thebonding material 636 (FIG. 37(D)). Here, by providing a plurality ofcapacitors 620 in the concave portion 734 having a flat base, theheights of the plural chip capacitors 620 are made uniform. Therefore,it is possible to form interlayer resin insulating layers 640 on thecore substrate 630 to have uniform thickness and to appropriately formvia holes 660 in later steps.

Then, the upper surfaces of the plural chip capacitors 620 are pressedor struck to thereby make the heights of the capacitors 620 uniform(FIG. 37(E)). Through this step, in providing a plurality of chipcapacitors 620 within the concave portion 734, the heights of the chipcapacitors 620 can be made completely uniform and the core substrate 630can be made smooth even if the sizes of the plural chip capacitors 620are uneven.

(3) Thereafter, a thermosetting resin is filled between the chipcapacitors 620 within the concave portion 734, heated and hardened tothereby form an interlayer rein insulating layer 633 (FIG. 38(A)). Asthe thermosetting resin, an epoxy resin, a phenol resin, a polyimideresin or a triazine resin is preferable. As a result, the chipcapacitors 620 within the concave portion 734 can be fixed. The resinlayer 633 having a lower coefficient of thermal expansion than that ofthe core substrate is employed.

Alternatively, a thermoplastic resin may be employed. It is alsopossible to impregnate filler in a resin so as to match the coefficientof thermal expansion. The filler involves, for example, inorganicfiller, ceramic filler, metal filler and the like.

(4) Further, using the printer, an epoxy resin or a polyolefin resin isapplied on the resultant substrate to thereby form a resin insulatinglayer 640 (FIG. 38(B)). Instead of applying a resin, a resin film may bebonded.

Alternatively, one type or more of a thermosetting resin, athermoplastic resin, a complex of a photosensitive resin, athermosetting resin and a thermoplastic resin, a complex of aphotosensitive resin and a thermoplastic resin and the like can beemployed. Two layers may be constituted using them.

(5) Next, openings 639 for relatively large via holes are formed in theresin insulating layer 640 by applying laser (FIG. 38(C)). Ade-smearprocess follows. Instead of applying laser, exposure and developmentprocesses can be performed. Holes 644 for through holes are formed inthe resin layer 633 by drilling or applying laser, heated and hardened(FIG. 38(D)). In some cases, a roughing process using an acid or anoxidizer or a roughing process by a plasma process may be performed. Bydoing so, the adhesiveness of the rough layers is ensured.(6) Thereafter, a copper plated film 729 is formed on the surface of theresin insulating layer 640 by electroless copper plating (FIG. 39(A)).Instead of electroless plating, sputtering may be conducted with Ni andCu as targets to form an Ni—Cu metal layer. Alternatively, after formingthe metal layer by sputtering, an electroless plated film may be formed.(7) Next, photosensitive dry films are bonded onto the surfaces of thecopper plated films 729, exposed and developed while mounting masks,thereby forming resists 649 each having a predetermined pattern. Thecore substrate 630 is immersed in an electroplating solution, current isapplied through the copper plated films 729 and electroplated plates 651are formed on portions on which the resists 649 are not formed (FIG.39(B)).(8) After separating and removing the plating resists 649 with 5% NaOH,the copper plated films 729 under the plating resists 649 are etched,dissolved and removed by a solution mixture of a sulfuric acid andhydrogen peroxide, thereby forming relative large via holes 660 andthrough holes 656 each having a filled via hole structure consisting ofthe copper plated film 729 and the electroplated copper film 651. Thediameters of the large via holes are preferably within a range of 100 to600 μm. The diameters are more preferably 125 to 350 μm. In this case,the large via holes are each formed to have a diameter of 165 μm. Thethrough holes are each formed to have a diameter of 250 μm. An etchingsolution is sprayed on the both sides of the substrate 630 to etch thesurfaces of the via holes 660 and the land surfaces of the through holes656, thereby forming rough surfaces 660 a on the entire surfaces of thevia holes 660 and the through holes 656 (FIG. 39(C)).(9) Thereafter, resin filler 664 mainly consisting of an epoxy resin isfilled in the through holes 656, and dried (FIG. 39(D)).(10) Thermosetting epoxy resin sheets each having a thickness of 50 μmare laminated by vacuum pressing on the both sides of the substrate 630which has been subjected to the above-stated steps, respectively, at apressure of 5 kg/cm² while raising temperature to 50 to 150° C. tothereby provide interlayer resin insulating layers 740 made of an epoxyresin (FIG. 40(A)). The degree of vacuum during vacuum pressing is 10mmHg. A cycloolefin resin instead of the epoxy resin can be employed.(11) Next, openings 642 for relatively small via holes are formed in theinterlayer resin insulating layers 740 having a thickness of 65 μm byapplying CO₂ gas laser (FIG. 40(B)). The diameters of the relativelysmall via holes are preferable in a range of 25 to 100 μm. Then, ade-smear process is performed using oxygen plasma.(12) Next, using SV-4540 manufactured by ULVAC JAPAN, Ltd., a plasmaprocess is performed to rough the surfaces of the interlayer resininsulating layers 740, thereby forming rough surfaces 646 (FIG. 40(C)).The plasma process is performed for two minutes while using, as inertgas, argon gas on conditions of power of 200 W, a gas pressure of 0.6 Paand a temperature of 70° C. The roughing process may be performed usingeither an acid or an oxidizer. The rough layers are preferably 0.1 to 5μm.(13) Next, after exchanging argon gas contained inside, using the samedevice, sputtering is performed on conditions of an atmosperic pressureof 0.6 Pa, a temperature 80° C., power of 200 W and a duration of 5minutes with Ni and Cu as targets and Ni—Cu metal layers 648 are formedon the surfaces of the interlayer resin insulating layers 740,respectively. At this time, the thickness of each of the formed Ni—Cumetal layers 648 is 0.2 μm (FIG. 40(D)). Plated films such aselectroless plated films may be formed or plated films may be formed onthe sputtered surfaces.(14) Commercially available photosensitive dry films are bonded onto theboth sides of the substrate 630 for which the above processes have beencompleted, photomask films are mounted thereon, the films are exposedwith 100 mJ/cm³ and then developed with a 0.8% sodium carbonatesolution, thereby providing plating resists 650 each having a thicknessof 15 μm. Then, electroplating is performed on the following conditions,thereby forming electroplated films 652 each having a thickness of 15 μm(FIG. 41(A)). It is noted that additive contained in an electroplatingsolution is Kaparacid HL manufactured by Atotech Japan.

[Electroplating Solution]

Sulfuric acid 2.24 mol/l Copper sulfate 0.26 mol/l Additive (KaparacidHL 19.5 mol/l manufactured by Atotech Japan)

[Electroplating Conditions]

Current density 1 A/dm² Duration 65 minutes Temperature 22 ± 2° C.(15) After separating and removing the resists 650 with 5% NaOH, theNi—Cu metal layers 648 under the plating resists are dissolved andremoved by etching using a solution mixture of a nitric acid, a sulfuricacid and hydrogen peroxide, thereby forming conductor circuits 758 eachconsisting of the Ni—Cu metal layer 648 and the electroplated film 652and a plurality of relatively small via holes 760 connected onto the viahole 660 (FIG. 41(B)). In this embodiment, the via hole 660 is formed tohave a filled via hole structure, thereby making it possible to directlyconnect a plurality of via holes 760 to the via hole 660.

Later steps are the same as those of (16) to (19) in the firstembodiment stated above, which description will not be, therefore, givenherein.

Next, description will be given to the mounting of the IC chip on theprinted circuit board 610 completed through the above-stated steps (FIG.42) and to the attachment of the printed circuit board to the daughterboard, with reference to FIG. 43. The IC chip 690 is mounted on theprinted circuit board 610 thus completed so that the solder pads 692 ofthe IC chip 690 correspond to the solder bumps 676U of the printedcircuit board 610 and a reflow process is performed, thereby mountingthe IC chip 690 on the printed circuit board 610. Likewise, a reflowprocess is performed so that the pads 694 of the daughter board 695correspond to the solder bumps 676D of the printed circuit board 610,thereby attaching the printed circuit board 610 to the daughter board695.

The above-stated resin contains a refractory resin, soluble particles, ahardening agent and other components, each of which is the same as thatdescribed in the first embodiment and will not be described herein.

First Modification of Fourth Embodiment

Next, a printed circuit board 612 according to the first modification ofthe fourth embodiment of the present invention will be described withreference to FIG. 52. In the fourth embodiment stated above, descriptionhas been given to a case of arranging the BGA. The first modification ofthe fourth embodiment is almost the same as the fourth embodiment.However, as shown in FIG. 52, the printed circuit board in thismodification is constituted into a PGA system establishing connectionthrough conductive connection pins 696.

Next, a method of manufacturing the printed circuit board stated abovewith reference to FIG. 32 will be described with reference to FIGS. 45to 52.

(1) First, a through hole 733 a for containing chip capacitors areformed in a multilayer plate 730 a constituted by providing four bondingresin layers 638 impregnated with an epoxy resin. Also, a multilayerplate 730β constituted by providing two bonding resin layers 638 isprepared (FIG. 45(A)). Here, as the bonding resin layers 638, thosecontaining a BT resin, a phenol resin or a reinforcing material such asglass cloth in addition to the epoxy resin can be employed.(2) Next, the multilayer plates 730 a and 730β are press-contacted witheach other, heated and hardened, thereby forming a core substrate 630provided with a concave portion 735 capable of containing a plurality ofchip capacitors 620 (FIG. 45(B)).(3) Then, using potting (dispenser), a bonding material 636 is appliedto the positions of the concave portion 735 at which the capacitors areto be arranged (FIG. 45(C)). Alternatively, the bonding material can beapplied to the concave portion by a printing method, a die-bondingmethod, a method of applying bonding sheets or the like. Thereafter, aplurality of chip capacitors 620 made of ceramic are contained in theconcave portion 735 through the bonding material 636 (FIG. 45(D)).(4) Then, a thermosetting resin is filled between the chip capacitors620 within the concave portion 735, heated and hardened, thereby forminga resin layer 633 (FIG. 46(A)). At this time, as the thermosettingresin, an epoxy resin, a phenol resin, a polyimide resin or a triazineresin is preferable. As a result, the chip capacitors 620 within theconcave portion 735 can be fixed.(5) Further, using a printer, the epoxy or polyolefin resin describedabove is applied onto the resultant substrate to thereby form a resininsulating layer 640 (FIG. 46(B)). Alternatively, a resin film may bebonded instead of applying a resin.(6) Next, openings 639 for relatively large via holes are formed in theresin insulating layer 640 by exposure and development processes or byapplying laser (FIG. 46(C)). The diameters of the relatively large viaholes are preferable in a range of 100 to 600 μm. Especially, therelatively large are preferable in a range of 125 to 350 μm. In thiscase, the via holes are each formed to have a diameter of 165 μm. Holes644 for through holes each having a diameter of 250 μm are formed in theresin layer 633 by drilling or by applying laser, heated and hardened(FIG. 46(D)).(7) A palladium catalyst is applied to the substrate 630. Then, the coresubstrate is immersed in an electroless plating solution to uniformlydeposit electroless plated films 745 (FIG. 47(A)). Then, resin filler isfilled in the openings 639 on which the electroless plated films 745 arerespectively formed, and dried. By doing so, a resin layer 747 is formedis each opening 639 (FIG. 47(B)).(8) Thereafter, photosensitive dry films are bonded to the surfaces ofthe electroless plated films 745, masks are mounted thereon, exposureand development processes are performed, thereby forming resists 649each having a predetermined pattern. The core substrate 630 is thenimmersed in an electroless plating solution, thereby forming platedcovers 751 each consisting of an electroless plated film (FIG. 47(C)).(9) After the above step, the resists 649 are separated with 5% NaOH.Thereafter, the electroless plated films 745 under the resists 649 areetched away with a solution mixture of a sulfuric acid and hydrogenperoxide, thereby forming relatively large via holes 661 of a filled viahole structure and through holes 656 (FIG. 47(D)). By constituting thevia holes 661 to have the filled via hole structure, it is possible todirectly connect a plurality of via holes 760 to one via hole 661 in astep to be described later.(10) After the substrate 630 is washed and degreased with an acid, thesubstrate 630 is subjected to soft-etching. Then, an etching solution issprayed on the both sides of the substrate 630 to etch the surfaces ofthe via holes 661 and the land surfaces and inner walls of the throughholes 656, thereby forming rough surfaces 663 on the entire surfaces ofthe via holes 661 and the through holes 656 (FIG. 48(A)). As the etchingsolution, an etching solution containing 10 parts by weight of animidazole copper (II) complex, 7 parts by weight of a glycolic acid and5 parts by weight of potassium chloride (MEC etch BOND manufactured byMec Compamy Ltd) is employed.(11) Next, 100 parts by weight of bisphenol F epoxy monomer (YL983Uhaving a molecular weight of 310 and manufactured by Yuka Shell), 170parts by weight of SiO₂ spherical particles having a surface coated witha silane coupling agent, having a mean particle diameter of 1.6 μm andhaving a maximum particle diameter of 15 μm or less (CRS 11-1-CEmanufactured by ADTEC) and 1.5 parts by weight of a leveling agent(PERENOL S4 manufactured by SANNOPCO) are stirred and mixed to therebyprepare resin filler 664 having a viscosity of 45 to 49 Pa·s at 23±1° C.As a hardening agent, 6.5 parts by weight of an imidazole hardeningagent (2E4MZ-CN manufactured by Shikoku Chemicals) is employed.

Thereafter, the resin filler 664 is filled in the through holes 656 anddried (FIG. 48(B)).

(12) Next, 30 parts by weight of a bisphenol A epoxy resin (Epicoat 1001having an epoxy equivalent of 469 and manufactured by Yuka Shell), 40parts by weight of a cresol novolac epoxy resin (Epichron N-673 havingan epoxy equivalent of 215 and manufactured by Dainippon Ink &Chemicals) and 30 parts by weight of a phenol novolac resin containingtriazine structure (Phenolight KA-7052 having a phenol hydroxyl groupequivalent of 120 and manufactured by Dainippon Ink & Chemicals) areheated and dissolved in 20 parts by weight of ethyl diglycol acetate and20 parts by weight of solvent naphtha while being stirred. Then, 15parts by weight of polybutadiene rubber having epoxy terminal (DenalexR-45EPT manufactured by Nagase Chemicals), 1.5 parts by weight ofpulverized 2-phenyl-4,5 bis(hydroxymethyl)imidazole, 2 parts by weightof particle-size reduced silica and 0.5 parts by weight of a silicondefoaming agent are added thereto, thus preparing an epoxy resincomposition.

The obtained epoxy resin composition is applied onto a PET film having athickness of 38 μm by using a roll coater so that the thickness of thefilm is 50 μm after the film is dried, and dried at 80 to 120° C. for 10minutes, thereby manufacturing resin films for interlayer resininsulating layers.

(13) The resin films for forming interlayer resin insulating layersslightly larger than the substrate 630 manufactured in (12) are mountedon the both sides of the substrate, respectively, temporarily pressed onconditions of a pressure of 4 kgf/cm², a temperature of 80° C. and apress duration of 10 seconds, and cut. Then, the resin films are bondedusing a vacuum laminator device by the following method, thereby forminginterlayer resin insulating layers 740 (FIG. 48(C)). Namely, theinterlayer resin insulating films are actually pressed on the substrate630 on conditions of the degree of vacuum of 0.5 Torr, a pressure of 4kgf/cm², a temperature of 80° C. and a press duration of 60 seconds andthen thermally hardened at 170° C. for 30 minutes.(14) Next, openings 642 for relatively small via holes of 65 μm areformed in the interlayer resin insulating layers 740 by applying CO₂ gaslaser through masks 757 in which penetrating holes 757 a each having athickness of 1.2 mm (FIG. 48(D)) are formed. The diameters of therelatively small via holes are preferably in a range of 25 to 100 μm.(15) The substrate 630 having the via hole openings 642 formed thereinis immersed in a solution containing 60 g/l of a permanganate acid at atemperature of 80° C. for 10 minutes and epoxy resin particles existingon the surfaces of the interlayer resin insulating layers 740 aredissolved and removed, thereby forming rough surfaces 646 on thesurfaces of the interlayer resin insulating layers 740 including theinner walls of the via hole openings 642 (FIG. 49(A)). The roughingprocess may be performed using an acid or an oxidizer. The roughsurfaces are preferably 0.5 to 5 μm.(16) Next, the substrate 630, for which the above stated processes havebeen completed, is immersed in a neutral solution (manufactured bySiplay) and washed. A palladium catalyst is applied to the surfaces ofthe substrate 630 which surfaces have been roughed (with a rough depthof 3 μm), thereby attaching catalyst cores on the surfaces of theinterlayer resin insulating layers 740 and the inner wall surfaces ofthe via hole openings 642.(17) Then, the substrate 630 is immersed in an electroless copperplating solution having the following composition to form electrolesscopper plated films 763 each having a thickness of 0.6 to 3.0 μm on theentire rough surfaces 646 (FIG. 49(B)).

[Electroless Plating Solution]

NiSO₄ 0.003 mol/l Tartaric acid 0.200 mol/l Copper sulfate 0.030 mol/lHCHO 0.050 mol/l NaOH 0.100 mol/l α,α′-bipyridyl   40 mg/l Polyethyleneglycol (PEG)  0.10 g/l

[Electroless Plating Conditions]

40 minutes at a solution temperature of 35° C.

(18) Commercially available photosensitive dry films are bonded onto theelectroless copper plated films 763, masks are mounted thereon,respectively and the films are exposed with 100 mJ/cm² and developedwith a 0.8% sodium carbonate solution, thereby providing plating resists650 each having a thickness of 30 μm. Then, the resultant substrate 630is washed with water of a temperature of 50° C. and degreased, washedwith water of a temperature of 25° C. and with a sulfuric acid, andsubjected to electroplating on the following conditions, thereby formingelectroplated copper films 652 each having a thickness of 20 μm (FIG.49(C)).

[Electroplating Solution]

Sulfuric acid 2.24 mol/l Copper sulfate 0.26 mol/l Additive 19.5 mol/l(Kaparacid HL manufactured by Atotech Japan)

[Electroplating Conditions]

Current density 1 A/dm² Duration 65 minutes temperature 22 ± 2° C.(19) After separating and removing the plating resists 650 with 5% NaOH,the electroless plated films 763 under the plating resists 650 areetched with a solution mixture of a sulfuric acid and hydrogen peroxide,removed and dissolved, thereby forming conductor circuits 758 andrelatively small via holes 760 each consisting of the electroless copperplated film 763 and the electroplated copper film 652 and having athickness of 18 μm (FIG. 49(D)). The same process as that in (10) isperformed, i.e., rough surfaces 622 are formed by employing an etchingsolution containing a cupric complex and an organic acid (FIG. 50(A)).(20) The steps of (13) to (19) are repeated, thereby forming interlayerresin insulating layers 741, conductor circuits 759 and via holes 764further above (FIG. 50(B)).(21) Next, a solder resist composition (an organic resin insulatingmaterial) is obtained in the same manner as that in the firstembodiment.(22) Then, the solder resist composition prepared in (21) is applied toeach side of the multilayer printed board to have a thickness of 20 μm.After a drying process is performed on conditions of 70° C. for 20minutes and 70° C. for 30 minutes, a photomask having a thickness of 5mm on which the pattern of solder resist openings are drawn, is closelyattached to each solder resist composition, exposure is performed withultraviolet rays of 1000 mJ/cm², development is performed with a DMTGsolution to thereby form openings 671U and 671D.

Thereafter, a heating process is performed to harden the solder resistcomposition on conditions of 80° C. for 1 hour, 100° C. for 1 hour, 120°C. for 1 hour and 150° C. for 3 hours to thereby harden the solderresist composition and form solder resist layers 670 each havingopenings 671U and 671D and having a thickness of 20 μm (FIG. 51(A)). Thesolder resist composition may be a commercially available solder resistcomposition.

(23) Then, the substrate 630 having the solder resist layers 670 formedthereon is immersed in the same electroless nickel plating solution asthat employed in the first embodiment, thereby forming a nickel platedlayer 672 in each of the openings 671U and 671D. Further, the substrateis immersed in the same electroless gold plating solution as thatemployed in the first embodiment, thereby forming a gold plated layer674 having a thickness of 0.03 μm on the nickel plated layer 672 (FIG.51(B)).(24) Thereafter, a solder paste containing tin-lead is printed on eachopening 671U of the solder resist layers 670 on the side of thesubstrate on which the IC chip is mounted. Further, a solder paste as aconductive bonding agent 697 is printed in each opening 671 on the otherside of the substrate. Next, conductive connection pins 696 are attachedto and supported by an appropriate pin holding device and the fixedportions 698 of the respective conductive connection pins 696 arebrought into contact with the conductive bonding agent 697 within theopenings 671D. After a reflow process is performed, the conductiveconnection pins 696 are attached to the conductive bonding agent 697.Also, to attach the conductive connection pins 696, the conductivebonding agent 697 may be formed into a ball shape or the like and put inthe openings 671D, or the conductive bonding agent 697 may be joined tothe fixed portions 698 to attach the conductive connection pins 696,followed by a reflow process.

Thereafter, the IC chip 690 is mounted on the printed circuit board 612so that the solder pads 692 of the IC chip 690 correspond to the opening671U side-solder bumps 676U of the printed circuit board 612, and areflow process is performed, thereby attaching the IC chip 690 (FIG.53).

Second Modification of Fourth Embodiment

A printed circuit board according to the second modification of thefourth embodiment of the present invention will be described withreference to FIG. 53. A printed circuit board 614 in the secondmodification of the fourth embodiment is almost the same as that in thefourth embodiment stated above. However, in the printed circuit board614 in the second modification of the fourth embodiment, one chipcapacitor 620 is contained in the concave portion 736 formed in the coresubstrate 630. Since the chip capacitor 620 is arranged within the coresubstrate 630, the distance between the IC chip 690 and the chipcapacitor 620 becomes short and loop inductance can be reduced.

Third Modification of Fourth Embodiment

Next, the constitution of a printed circuit board according to the thirdmodification of the fourth embodiment will be described with referenceto FIG. 14.

The printed circuit board in the third modification is almost the samein constitution as the printed circuit board in the first embodimentstated above. They, however, differ in chip capacitors 20 contained inthe core substrate 30. FIG. 14 is a plan view of chip capacitors. FIG.14(A) shows a chip capacitor before being cut for providing a pluralityof chip capacitors. In FIG. 14(A), a dashed line denotes a cut line. Asshown in FIG. 14(B), in the printed circuit board in the firstembodiment stated above, the first electrodes 21 and the secondelectrodes 22 are provided on the edges of the chip capacitor. FIG.14(C) shows a chip capacitor before being cut for providing a pluralityof chip capacitors in the third modification. In FIG. 14(C), a dashedline denotes a cut line. In the printed circuit board in the thirdmodification, as shown in the plan view of FIG. 14(D), first electrodes21 and second electrodes 22 are provided inside of the edges of the chipcapacitor.

In the printed circuit board in the third modification, the chipcapacitors 20 each having electrodes formed inside of the outer edgesthereof are employed, so that mass storage chip capacitors can beemployed.

Next, a printed circuit board according to the first other example ofthe third modification will be described with reference to FIG. 15.

FIG. 15 is a plan view of a chip capacitor 20 contained in the coresubstrate of the printed circuit board according to the first otherexample. In the first embodiment stated above, a plurality of smallstorage chip capacitors are contained in the core substrate. In thefirst other example, by contrast, a large, mass storage chip capacitor20 is contained. The chip capacitor 20 consists of the first electrodes21, the second electrodes 22, a dielectric 23, first conductive films 24connected to the first electrodes 21, second conductive films 25connected to the second electrodes 22, electrodes 27 which are notconnected to the first and second conductive films 24 and 25, for theconnection of the upper and lower surfaces of the chip capacitor. The ICchip and the daughter board are connected to each other through theelectrodes 27.

Since the large chip capacitor is employed in the printed circuit boardin the first modification, it is possible to employ a mass storage chipcapacitor. Further, since the large chip capacitor 20 is employed, theprinted circuit board does not warp even if a heat cycle is performedrepeatedly.

A printed circuit board according to the second other example of thesecond modification will be described with reference to FIG. 16. FIG.16(A) shows a chip capacitor before being cut for providing a pluralityof chip capacitors. In FIG. 16(A), a dashed line denotes an ordinary cutline. FIG. 16(B) is a plan view of the chip capacitors. As shown in FIG.16(B), a plurality of (or in FIG. 16(B), three) chip capacitors forproviding multiple capacitors are coupled to one another and employed asa large capacitor as a whole.

In the second other example, since the large chip capacitor 20 isemployed, it is possible to employ a mass storage chip capacitor.Further, since the large chip capacitor is employed, the printed circuitboard does not warp even if a heat cycle is performed repeatedly.

In the embodiment stated above, the chip capacitors are built in theprinted circuit board. Alternatively, plate-like capacitors eachconstituted by providing a conductive film on a ceramic plate may beemployed instead of the chip capacitors.

Further, in the fourth embodiment stated above, only the chip capacitorscontained in the core substrate are provided. Alternatively, massstorage chip capacitors can be mounted on the front and reverse sides ofthe substrate as in the case of the first other example of the firstembodiment.

As described above with reference to FIG. 12, voltage variation can beminimized by providing the chip capacitors 20 in the vicinity of the ICchip and the mass storage chip capacitors (having relatively highinductance) on the front and reverse sides.

Now, as for the printed circuit board in the fourth embodiment, themeasurement values of the inductance of the chip capacitor 620 embeddedin the core substrate and that of the chip capacitor mounted on thereverse side (daughter board side-surface) of the printed circuit boardare shown below.

In a case where a single capacitor is used:

Embedded type 137 pH Reverse side mounted type 287 pHIn a case where eight capacitors are connected in parallel:

Embedded type 60 pH Reverse side mounted type 72 pH

As can be understood from the above, it is possible to reduce inductanceby including the chip capacitor(s) regardless of whether a singlecapacitor is used or capacitors are connected in parallel so as toincrease storage capacity.

Next, the result of a reliability test will be described. Here, the rateof change of the capacitance of one chip capacitor on the printedcircuit board in the fourth embodiment was measured.

Rate of Change of Capacitance (measurement (measurement frequency 100Hz) frequency 1 kHz) Steam  168 hours 0.3% 0.4% HAST  100 hours −0.9%−0.9% TS 1000 cycles 1.1% 1.3%

In the Steam test, a humidity of 100% was maintained by applying steam.In the HAST test, the chip capacitor was left at a relative humidity of100%, an applied voltage of 1.3 V and a temperature of 121° C. for 100hours. In the TS test, tests for leaving the capacitor at −125° C. for30 minutes and 55° C. for 30 minutes were repeated 1000 times.

As a result of the above-stated reliability test, it was discovered thatthe printed circuit board including the chip capacitor(s) therein canattain equivalent reliability to that of the existing capacitor surfacemount type. Further, as a result of the TS test, it was discovered thateven if an internal stress occurs due to the difference in thecoefficient of thermal expansion among the capacitors made of ceramic,the core substrate made of a resin and the interlayer resin insulatinglayers, disconnection does not occur between the electrodes of the chipcapacitors and the via holes, separation does not occur between the chipcapacitors and the interlayer resin insulating layers and cracks do notoccur to the interlayer resin insulating layer, whereby high reliabilitycan be attained for a long time.

With the constitution of the fourth embodiment, the via holes in thefourth embodiment are formed between the conductor circuits and thecapacitors. Due to this, it is possible to maintain desired performancewithout delaying operation due to lack of power supply and no problemsarose even if a reliability test was conducted.

Moreover, because of the via holes, even if the via holes are formed inthe interlayer resin insulating layers and positional errors occur tothe via holes, the allowance is wide. Thus, electrical connectioncharacteristics can be ensured.

1. (canceled)
 2. A method for manufacturing a printed circuit board,comprising: forming an opening portion in a substrate; positioning aplurality of chip capacitors in the opening portion of the substratesuch that the plurality of chip capacitors is accommodated in theopening portion of the substrate; forming a buildup structure comprisingan interlayer resin insulating layer and a conductive layer over asurface of the substrate and the plurality of chip capacitorsaccommodated in the opening portion of the substrate; and forming on asurface of the buildup structure a plurality of bump structurespositioned to mount an IC chip such that the plurality of chipcapacitors in the opening portion of the substrate is positioneddirectly below the IC chip.
 3. A method for manufacturing a printedcircuit board according to claim 2, further comprising forming aplurality of via conductors in the buildup structure such that the viaconductors connect the plurality of bump structures and the plurality ofchip capacitors through the buildup structure, wherein the openingportion of the substrate is a concave portion formed in the substrate.4. A method for manufacturing a printed circuit board according to claim2, further comprising: forming a through hole in a first resin plate;and bonding a second resin plate to the first resin plate such that thesubstrate having the opening portion is formed.
 5. A method formanufacturing a printed circuit board according to claim 2, wherein theforming of the buildup structure includes forming a plurality of firstvia conductors connected to a plurality of electrodes of the pluralityof chip capacitors, respectively, and forming a plurality of second viaconductors on the plurality of first via conductors, respectively, suchthat the plurality of second via conductors is connected to theplurality of first via conductors, respectively, and that each of thesecond via conductors has a via diameter which is smaller than a viadiameter of each of the first via conductors, and the plurality of firstvia conductors is a plurality of filled via conductors each comprising aplated material and having a flat upper surface.
 6. A method formanufacturing a printed circuit board according to claim 2, wherein theforming of the buildup structure includes forming a plurality of firstvia conductors connected to a plurality of electrodes of the pluralityof chip capacitors, respectively, and forming a plurality of second viaconductors on the plurality of first via conductors, respectively, suchthat the plurality of second via conductors is connected to theplurality of first via conductors, respectively, and that each of thesecond via conductors has a via diameter which is smaller than a viadiameter of each of the first via conductors, and each of the first viaconductors is formed by filling a hole formed in the interlayerinsulating layer with a plated material.
 7. A method for manufacturing aprinted circuit board according to claim 3, further comprising: applyinga pressure to upper surfaces of the chip capacitors accommodated in theopening portion of the substrate such that the plurality of chipcapacitors has uniform heights of the upper surfaces of the chipcapacitors.
 8. A method for manufacturing a printed circuit boardaccording to claim 2, further comprising forming a plurality of viaconductors in the buildup structure such that the via conductors connectthe plurality of bump structures and the plurality of chip capacitorsthrough the buildup structure.
 9. A method for manufacturing a printedcircuit board according to claim 2, wherein the forming of the buildupstructure includes forming a plurality of via conductors connected to aplurality of electrodes of the plurality of chip capacitors,respectively.
 10. A method for manufacturing a printed circuit boardaccording to claim 2, wherein the forming of the buildup structureincludes forming a plurality of first via conductors connected to aplurality of electrodes of the plurality of chip capacitors,respectively, and forming a plurality of second via conductors on theplurality of first via conductors, respectively, such that the pluralityof second via conductors is connected to the plurality of first viaconductors, respectively.
 11. A method for manufacturing a printedcircuit board according to claim 2, wherein the forming of the buildupstructure includes forming a plurality of first via conductors connectedto a plurality of electrodes of the plurality of chip capacitors,respectively, and forming a plurality of second via conductors on theplurality of first via conductors, respectively, such that the pluralityof second via conductors is connected to the plurality of first viaconductors, respectively, and that each of the second via conductors hasa via diameter which is smaller than a via diameter of each of the firstvia conductors.
 12. A method for manufacturing a printed circuit boardaccording to claim 2, wherein the forming of the bump structurescomprises forming a plurality of solder bump structures on the surfaceof the buildup structure.
 13. A printed circuit board, comprising: asubstrate having an opening portion; a plurality of chip capacitorspositioned in the opening portion of the substrate such that theplurality of chip capacitors is accommodated in the opening portion ofthe substrate; a buildup structure comprising an interlayer resininsulating layer and a conductive layer and formed over a surface of thesubstrate and the plurality of chip capacitors accommodated in theopening portion of the substrate; and a plurality of bump structurespositioned to mount an IC chip on a surface of the buildup structuresuch that the plurality of chip capacitors in the opening portion of thesubstrate is positioned directly below the IC chip.
 14. A printedcircuit board according to claim 13, wherein the buildup structure has aplurality of via conductors formed in the buildup structure such thatthe via conductors connect the plurality of bump structures and theplurality of chip capacitors through the buildup structure, and theopening portion of the substrate is a concave portion formed in thesubstrate.
 15. A printed circuit board according to claim 13, whereinthe substrate has a through hole in a first resin plate and a secondresin plate bonded to the first resin plate such that the substrate hasthe through hole forming the opening portion.
 16. A printed circuitboard according to claim 13, wherein the buildup structure has aplurality of first via conductors connected to a plurality of electrodesof the plurality of chip capacitors, respectively, and a plurality ofsecond via conductors formed on the plurality of first via conductors,respectively, such that the plurality of second via conductors isconnected to the plurality of first via conductors, respectively, andthat each of the second via conductors has a via diameter which issmaller than a via diameter of each of the first via conductors, and theplurality of first via conductors is a plurality of filled viaconductors each comprising a plated material and having a flat uppersurface.
 17. A printed circuit board according to claim 13, wherein thebuildup structure has a plurality of first via conductors connected to aplurality of electrodes of the plurality of chip capacitors,respectively, and a plurality of second via conductors formed on theplurality of first via conductors, respectively, such that the pluralityof second via conductors is connected to the plurality of first viaconductors, respectively, and that each of the second via conductors hasa via diameter which is smaller than a via diameter of each of the firstvia conductors, and each of the first via conductors comprises a platedmaterial filling a hole formed in the interlayer insulating layer.
 18. Aprinted circuit board according to claim 13, wherein the plurality ofchip capacitors has uniform heights of surfaces of the chip capacitors.19. A printed circuit board according to claim 13, wherein the buildupstructure has a plurality of via conductors formed in the buildupstructure such that the via conductors connect the plurality of bumpstructures and the plurality of chip capacitors through the buildupstructure.
 20. A printed circuit board according to claim 13, whereinthe buildup structure has a plurality of via conductors connected to aplurality of electrodes of the plurality of chip capacitors,respectively.
 21. A printed circuit board according to claim 13, whereinthe buildup structure has a plurality of first via conductors connectedto a plurality of electrodes of the plurality of chip capacitors,respectively, and a plurality of second via conductors formed on theplurality of first via conductors, respectively, such that the pluralityof second via conductors is connected to the plurality of first viaconductors, respectively.
 22. A printed circuit board according to claim13, wherein the buildup structure has a plurality of first viaconductors connected to a plurality of electrodes of the plurality ofchip capacitors, respectively, and a plurality of second via conductorsformed on the plurality of first via conductors, respectively, such thatthe plurality of second via conductors is connected to the plurality offirst via conductors, respectively, and that each of the second viaconductors has a via diameter which is smaller than a via diameter ofeach of the first via conductors.
 23. A printed circuit board accordingto claim 13, wherein the plurality of bump structures is a plurality ofsolder bump structures formed on the surface of the buildup structure.